### Linear algebra applications

I spent the last month at the chalet in Petkovo, the village where my grandfather is from. Check out the view from my office:

I have good progress to report on the linear algebra book. Sandy (my editor) has gone through the first few chapters and looks on track to finish editing the book by the end of October, which means the NO BS guide to LA will be available in print soon.

On my side, I’ve been working on the applications chapter. In this chapter I discuss all the cool things you can do using linear algebra. The topics covered include linear programming, error correcting codes, solving for the voltages in electric circuits, and other applications to economics and science. It really feels good to be able to discuss all these applications, and substantiate the claim I make in the book’s introduction, namely, that learning linear algebra will open many doors for the reader.

In other news, I think I’ve finally found a civilized way to generate html and .epub versions of the book: polytexnic, which is part of the softcover platform for self-publishers. Here’s a quote from the documentation:

The real challenge is producing EPUB and MOBI output. The trick is to (1) create a self-contained HTML page with embedded math, (2) include the amazing MathJax JavaScript library, configured to render math as SVG images, (3) hit the page with the headless PhantomJS browser to force MathJax to render the math (including any equation numbers) as SVGs, (4) extract self-contained SVGs from the rendered pages, and (5) use Inkscape to convert the SVGs to PNGs for inclusion in EPUB and MOBI books. Easy, right? In fact, no—it was excruciating and required excessive amounts of profanity to achieve. But it’s done, so ha.

Stay tuned for .epub version of the books in the No BS guide series.

### The economics of writing books people want

I just saw this article on priceonomics about profits from books(via HN). It hits some facts right on the nail, gets others wrong, and finally misses the main point. Let me quote here the best parts (with comments) and give you my interpretation of what print-on-demand and ebooks will bring about.

With publishing houses only offering a royalty rate of between 6-15%.

Let’s say more like 2%–5% because this is from the *profits*, not a percentage of the sale price.

Email marketing was critical.

You got that right!

Self-publishing is arguably a wonderful innovation. It is historically unprecedented, providing the means for millions of people around the world to bypass the elitism of the publishing establishment […] In terms of access to a worldwide marketplace, it is fantastically democratic. In terms of access to financial success, it is far from it.

The OP misunderestimates the power of a democratic marketplace. There is a process of natural selection for book products. It used to act on a time scale of years and decades in the old days, but with the ease that information spreads now, I predict increased competition on the marketplace and unprecedented advances in book quality. As authors start to earn money from writing books, better books will be written. Also, the higher margins of self-publishing (think 50%) make solo authors and mini-publishers much more competitive that the old dinosaurs.

It is my hope that if books become better, more youth will escape their brain being crushed like a jujube by fast-moving pixels activities and learn to think bigger thoughts—hopefully constructive ones. Could an increase in interest in books bring about a new golden age of reason?

That would definitely be nice; enough with the consumerism, warring, and financial schemes. Let’s have another renaissance or something…

Sometime in mid-December I set out to create problem sets for the book. My friend Nizar Kezzo offered to help me write the exercises for Chapter 2 and Chapter 4 and I made a plan to modernize the calculus questions a bit and quickly write a few more questions and be done in a couple of weeks.

That was four months ago! Clearly, I was optimistic (read unrealistic) about my productivity. Nizar did his part right on schedule, but it took me forever to write nice questions for the other chapters and to proofread everything. After all, if the book is no bullshit, the problem sets must also be no bullshit. I’m quite happy with the results!

noBS problem sets: letter format or 2up format.

Please, if you find any typos or mistakes in the problem sets, drop me a line so I can fix them before v4.1 goes to print.

### Tools

In addition to work on the problem sets, I also made some updates to the main text. I also developed some scripts to use in combination with latexdiff to filter only pages with changes. This automation saved me a lot of time as I didn’t have to page through 400pp of text, but only see the subset of the pages that had changes in them.

If you would like to see the changes made to the book from v4.0 to v4.1 beta, check out noBSdiff_v4.0_v4.1beta.pdf.

### Future

Today I handed over the problems to my editor and once she has taken a look at them, I’ll merge the problems into the book and release v4.1. The coming months will be focussed on the business side. I know I keep saying that, but now I think the book is solid and complete so I will be much more confident when dealing with distributors and bookstores. Let’s scale this!

### Opportunity costs

Recently, after conversations with friends who work in industry, I’ve been questioning my “career strategy” of pursuing a textbook publishing startup. Generally speaking, the employability of a new graduate is at its peak at graduation. Industry accepts young CS graduates and tells them “Here is 70k, write this code for us” and after a few years they could be pulling in 130+k, which is prof-level income. Regardless of one’s future goals in life a little injection of cash for a person in their thirties sounds like a good thing to have. In general working is a good career move.

Using the language of economics there are opportunity costs of doing the startup thing. First there is the short term financial losses of not having a San Francisco software developer salary right now. Second, and perhaps more importantly, I may be sabotaging my career options should I ever decide to go to industry. Recruiters will ask “what did you do for the past two years?” So doing the startup thing (i.e. not doing the corporate thing) has multiple opportunities costs.

Though such thoughts do turn around in my head, I remained and remain undeterred. I just realized why—this is the inspiration for this post. There are opportunity costs with the corporate career too. This knowledge that I have fresh in my mind after teaching undergraduate math and physics for the last ten years will soon be forgotten. Certainly after two years in industry, I would not remember half the things I can recall off the top of my head right now.

So this is why, now I know, I subconsciously chose this path. We godda do this now and we’ll code later, si besoin.

Aside: I just previewed the latest linear algebra draft and it looks awesome! I’ve been slogging through the corrections during the past couple of weeks (actually months!) and I was feeling low on energy, but now that I see how close we are to the finished product I’m getting all enthusiastic again.

### Open book writing and typo workflow

Open is better than closed because when you work in the open the whole world can help you (or at least the portion of the world that cares about what you are doing). For books in particular, readers can be tremendously helpful by submitting typo fixes to the book. But how can users submit typos? Surely there is something better than email…

Today I saw a very interesting workflow for reader contributions on the Advanced R programming book website by Hadley Wickham. The book  is being developed on github using the Jekyll static site generator. Each page has an “Edit this” link on the right side:

The url for that button is:

https://github.com/hadley/adv-r/edit/master/index.rmd

Clicking on that takes you to github and a special prompt to create a fork:

Next you can make the change:

And finally the UI offers you to do a pull request:

This is still a complicated process for the reader (3-steps, one feature branch, one pull request), but from the author side this is awesome! You just write and then manage incoming pull requests that improve your content.

Anyone writing their blog posts in the open on github should consider adding the /edit/ links.

Weekend project: find a way to automate this workflow process so readers don’t need to have github accounts. Maybe I could create a “shared” github account “ivans-readers,” allow for login-less-editing to happen on my own server and then see the pull requests coming from ivans-readers on the main repo.

### Techzing interview

Earlier this year I launched my book on hacker news which resonated very positively with the hacker crowd.  This HN exposure landed me an  interview on the TechZing podcast  to discussed my textbook project. Even though it was an hour and a half long interview, there were a some things that we didn’t get to discuss. I want to take the moment now to write down my observations about the textbook business and the educational market.

This blog post is organized with the best stuff at the top so feel free to trail off at any point.

### Insights

1. Writing is tough, but writing down lecture notes after a lecture is easy.
2. Teaching students is gold. By interacting with your students 1-on-1 you get feedback on your explanations.
If you are lucky you will get a “Sorry, I didn’t get that”, which allows you to iterate.
3. People still appreciate the printed book. Some people are willing to pay good money for a PDF.

### Opportunities

Print-on-demand and eBook technology allow for everyone to publish and sell books. This is a revolution on a Gutenberg scale. One of the forefathers of the Internet/WWW, when asked about the motivation behind his inventions said he did it “so people will be able to earn a living from the fruits of their intellectual labour.”  We have now finally reached this moment where this idea is practical.  Could books be the missing monetization strategy for the Internet?

What have been traditionally two markets—the general audience and the educational market—are now becoming a single market of people who want to learn. Lord knows there are things to learn out there so there is an opportunity for knowledge products for people who want to learn. The key monetization routes will be through selling organized knowledge as textbooks, ebooks, or apps.

I used the term revolution above and I stand by this choice of wording because this is what we call it when a value chain collapses from six-plus levels to three levels. The value chain in the “book business” previously looked like this:

author
__editor
__copy-editor
__typesetter
__printer
__distributor[1..]
__book store
__client

With print-on-demand the new book business will look like this:


author -- printer -- shipping -- client
^^^^^^                           ^^^^^^


Let us call this “author centered” publishing. From now on, authors can expect to get up to 50% of the profits instead of 10% (which could be as low as 5% of the list price). Good times for authors. Incentive-giving-to-move-to-a-new-publisher times.

Even amazon looks like a dinosaur in this context:

author
__editor
__copy-editor
__typesetter
__printer
__amazon
__shipping
__client


Why do you need the warehouse to store all the books? Why not ship from the printer?

There is one element in the traditional publishing value chain that we must keep. Copy editing is actually very important because you really want someone to go through
your writing and fix mistakes in it. You can use your target audience (crowdsource copy-editing), but nothing beats professional services.

OK, so you want to see the future of publishing? Here it is:

 author -- (1) pub.srvc. -- (2) printer  -- shipping -- client
_ (3) booksite -- client

The opportunities are (1) for small publishing houses (copy editor + creative person for covers + latex guy) to really come-in and take over the entire market within a couple of years. You could also have larger publishers who focus on marketing the book to certain audiences etc.

Opportunity (2) is for new print-on-demand shoppes to come up (compete with lulu.com and lightning source). These giants have as their main advantage the established processes they have in place, but how difficult would it be to build an “Espresso Book Machine”-like system based on a quality BW laser printer (think buying toner in gallon tubes at costco 😉 and some automation. The competitive advantage of a small print shop would be that they offer pick up service (0\$shipping). Currently lulu charges you 6\$ for shipping to Canada (9\$for 2 books, 12\$ for three books, …, 3+3n.) Shipping within the states is \$5 which is better, but still not free. In particular for printing small books (100-200pp) it would not make sense to order from lulu. They would charge you 5\$ for the printing and another 6\$for the shipping. Your cost 11\$. If you go to a local print shoppe, they will charge you 7\$for printing. Same product, half price. The third opportunity is for high-level editorial services (think curation of content) which would collect book recommendations and let authors and readers interact. Ideally there should be independent “book blogs” for discovery of new content — not marketplaces. Something must be done about the current appstore monopoly. Every app you develop relying on Apple for your distribution is feeding the monster at 30%. Every web app you develop based on Google or FB apis could stop working tomorrow if the API is retired. Go get hosting somewhere and build your own website. Don’t depend on anyone. Okay sorry I got a little off the topic of textbooks. Let’s get back on topic. I was telling you guys about the book and stuff from the interview. One thing which we talked a lot about was the hacker news launch. ### The HN launch I told Jason how surprized I was when I got 30 000 visitors in one day and how I didn’t get up from my chair for one day. There were roughly 7000 people who clicked on one of the modals. Of these 300 people bought the book in print. By the evening of Jan 1st and into Jan 2nd there were also 100 PDFs purchased from gumroad. I still working out the numbers (conversion rates) and I don’t want to get too hyped up about them (ok ok, 7k –> 300 = 4.3%) because the HN audience is really VERY sympathetic to the product. I am not sure if everyone else on the internet will like it as much. (SIDENOTE: I am finding it hard to get the analytics I want for the book pageGA reports analytic en masse so I cannot see what individual visitors did when they came to the site. I have basic questions I need answers for and it seems like the current state of analytics is very unimpressive (relative to my expectations). Here is what I would like to know: 1. Which modal my visitors looked at before deciding to continue onto lulu.com/shop or gumroad? 2. Which of the 800 people who clicked through to lulu.com/shop are the 300 that actually ended up buying the book? 3. Which sections did they read (scroll to and stay for 4secs+)? 4. What “path” did each visitor follow through the modals? (subquestion: did anyone see the apg-get install mechanics? did anyone see the integral calculus modal? ) Are there solutions for these? I think the only way I can have end-to-end information is if I run the whole show. If I want to have information about converstions I must build my own shopping cart. Wait, we are on the Internet — I can just submit a feature request to lulu.com support and gumroad support. I am working on the full writeup of the launch experience here which will have more graphs and numbers. (/SIDENOTE) I got a lot of feedback from the discussion on hacker news. People really like the idea. The tech crowd of Hacker News is precisely the kind of crowd is interested in learning about advanced math and physics. Many programmers learn the about calculus in mechanics at University but never actually understood these subjects. This is way when the no bullshit guide to mass in physics the really wanted and the 29 dollars price range is definitely not an obstacle for them. Several people also asked for a PG 13 version cleaned up with out of cities in the references to park and alcohol. This is definitely something I will look into it because no told jokes need to be about these subjects. We can stick to the political stuff and the joke about the investment banker being dropped off a building. What is the goal of the book? The goal of the book and more generally of Minireference Co. is to teach. Teach students how to get rid of the exam stress when they’re doing their studies. If you know the material really well, then there is nothing tricky that the teacher can do on the final. Understanding trumps memorization any day of the week. A secondary goal is to teach math to adults, grown ups, so they can let go of their math complexes. There is no reason why a forty year old person should avoid conversations about math and feel uncomfortable when their teenage daughter or son asks them about the solutions to a quadratic equation. The third goal is to prevent the next generation of analytic reminded youth from going into the defence, pharmaceutical and finance sectors, which I consider to be detrimental to society. I grew up listening to Rage Against the Machine and I feel it is my duty to continue their work in educating the next generations about the system. By situating analytical knowledge in the context of the current world geopolitical situation, it is my hope that the next generation of Einsteins, Gates, Pages, and Zuckerbergs will make informed and moral choices. With knowledge comes responsibility, and I don’t want my students to think about the numbers without understanding what the numbers represent in the real world. ### Textbook market There are a couple of intrenched companies in the publishing world (the big five). Mainstream publishers in the educational market produce textbook that are so expensive, that we can talk about a textbook racket. The readers, subject to their teachers authority, are forced to buy specific textbooks, often at an exorbitant prices > \$100. Mainstream textbooks are also too long and full of fluff like full-page photos designed to pad the pages and impress the student with the “high endness” of the 1000-page publication.  Mainstream textbooks are the kind of product which is the signed by committee. They’re thick and boring.

On the other hand there are several positive things about textbooks.  Irrespective of the widened usage of electronic formats, the “book format” remains the primary medium of intellectual discourse, of which textbooks are a subset. Textbooks are old technology, but good technology. Textbook, as a mean for acquiring knowledge, are better than most educational resources produced for the web.  And it’s not just eBooks, print is here to stay because students don’t like the idea of ebooks replacing textbooks.  Having a PDF to go along with your printed textbook is definitely a feature, but not as a replacement.

The business model for Minireference Publishing Co. is quite simple: we sell math and science textbooks and PDFs. The specifics of the book “container” are not important. What is important and of value is that we offer an “information distillation” service: complicated science subjects are presented and explained in a concise coherent narrative, including all prerequisites. Instead of reading 100 wikipedia pages to learn about calculus in a month, students can read one chapter in the No BS guide and pick up the same material in a week.

Backstory

During the interview, I had a chance to give the full story about the genesis of the book. At 7min40sec in the interview, I say how I started from a collection of notes on advanced physics subjects and that at some point decided to make those notes into a book. Jason replies to this jokingly “Wow that is a big jump!” but I totally missed his joke and just kept on blabbing.

Pivot 1: TOO ADVANCED. There are not that many physicists. We need to go for something more mainstream. New product will be a mini-reference book of formulas for all of science.

Pivot 2: FORMULAS ARE NOT ENOUGH to learn. Let’s have the formulas, but add enough context and explanations to explain where the formulas come from and how they are used.

Once you have the idea… It took two years and 200 commits. It wasn’t high intensity work: I just wrote down lecture notes and my favourite explanations after teaching. During the summer of 2012, I worked intensely to tie together and organize all the material into a coherent story with a beginning (solving equations), a middle (use equations to predict the motion of objects in physics), and an end (learn where the equations of physics arise from calculus).

### Product

What is special about this book is the deed forms contains a complete dependency graph of topics. Each subject is explain along with all the prerequisite material.

Another thing special about the book is its conversational tone. The narration in the book switches from serious to joke mode and back to serious again, and is intended to keep the reader engaged.  Everyone needs a little brake after learning pages and pages of formulas…

### Technology used

During the interview, I didn’t get a chance to discuss the technology stack I used to generate the book. The book started as a bunch of text file in dokuwiki. I then used the dokutexit plugin to export the book as LaTeX.

Another important tool for the production of the book has been to use the text-to-speech tool in Mac OS X for proofreading. It allowed me to catch lots of mistakes and quickly.

I use lulu.com for print-on-demand and gumroad.com for the PDF distribution.

### Future

Some future directions for the development of the book are:

• Finish the linear algebra textbook
• Write Tome II on electricity and magnetism and vectors calculus
• Future plans: Write a book about probability and stats
• Future plans: Make a No BS guide to Python and JavaScript

Speaking of JavaScript I’m currently exploring the using khan-exercises framework so I could offer practice problems on the site.

The main challenges we face right now is marketing the book to a wide audience.

UPDATE: Since the publication of this post, the No Bullshit guide to math and physics has been improved and revised several times. Sales going Okay. Need more word of mouth

### Strang lectures on linear algebra

Professor Gilbert Strang’s video lectures on Linear Algebra have been recommended to me several times. I am very impressed with the first lecture. He presents all the important problems and concepts of LA in the first lecture and in a completely as-a-matter-of-fact way.

The lecture presents the problem of solving n equations in n unknowns in three different ways: the row picture, the column picture and the matrix picture.

In the row picture, each equation represents a line in the xy plane. When “solving” these equations simultaneously, we are looking for the point (x,y) which lies on both lines. In the case of the two lines he has on the board (2x-y=0 and -x+2y=3) the solution is the point x=1, y=2.

The second way to look the system of equations is to think of the column of x coefficients as a vector and to think of the column of y coefficients as another vector. In the column picture, solving the system of equations requires us to find the linear combination of the columns (i.e., $x$ times the first column plus $y$ times the second column) gives us the vector on the right hand side.

If students start off with this picture, they will be much less mystified (as I was) by the time they start to learn about the column space of matrices.

As a side benefit of this initial brush with linear algebra in the “column picture”, Prof. Strang is also able to present an intuitive picture for the formula for the product between a matrix and a vector. He says “Ax is the combination of the columns of A.”  This way of explaining the matrix product is much more intuitive than the standard dot-product-of-row-times-column approach. Who has seen them dot products? What? Why? WTF?

I will definitely include the “column picture” in the introductory chapter on linear algebra in the book. In fact, I have been wondering for some time how I can explain what the matrix product Ax. I want to talk about A as the linear transformation TA so that I can talk about the parallels between $x$, $f:R \to R$, $f^{-1}$ and $\vec{v}$, $A$, $A^{-1}$. Now I know how to fix the intro section!

Clearly you are the master of the subject. It is funny that what started as a procrastination activity (watching a youtube video to which I just wanted to link to) led to an elegant solution to an old-standing problem which was blocking my writing. Sometimes watching can be productive 😉  Thank you Prof. Strang!

### Abstract

Calculus and mechanics are often taught as separate subjects. It shouldn’t be like that. If you learn calculus without mechanics, it will be boring. If you learn physics without calculus, you won’t truly understand.

I think I may have found a way to solve this chicken and egg problem. It goes a little something like this:

1. Chapter 1. You need [solving_equations,algebra,quadratic_equation] to do physics. That is all the prerequisites for first year Physics.
2. Chapter 2. Physics laws are expressed as equations. If you know how to solve equations, then you know how to solve physics equations. In particular we will study the kinematics equations $x(t)$, $v(t)$, $a(t)$, which describe the motion of an object.
• Start by defining kinematics concepts like time $t$, position $x(t)$, velocity $v(t)$, acceleration $a(t)$, initial position $x_i$, and initial velocity $v_i$. We can then state the UAM equations straight up: $a(t)=a$, $v(t)=v_i+at$, $x(t)=x_i+v_it+\frac{1}{2}at^2$. Example (free fall): An object on which only the force of gravity acts is said to be in free fall. Such objects experience a constant downwards acceleration of magnitude 9.81[$m/s^2$].  The classic examples are a ball thrown in the air. Using equations you can calculate the trajectory of the ball, and predict where it will land. Equations are cool and all, but where do these equations come from?In order to find out we must take a short excursion into calculus-land.
• Calculus is the study of functions. We use calculus in to describe how quantities change over time (derivatives $f'(t)$) or to find the total amount of quantities that vary over time (integration $F = \int f \;dt$). Integrals sound fancy, but are really just a an area-under-the-curve calculation. Provide visual proofs for two important cases: if $f(t)=3$, then $F(t)=3t$. If $g(t)=t$, the integral is $G(t)=\frac{1}{2}t^2$.But why should anyone care about integrals?  What good is computing the area under a curve?
• Integrals are the inverse operation of the derivative. In analogy with the inverse functions that we use when solving equations, the concept of an inverse operation is a useful concept in calculus: integrals are the inverse operations of derivatives.The kinematics equations of that describe the motion of objects can be derived from Newton’s law $F=ma$ and applying the integration operation twice. This is easy to see: we start by rewriting $F=ma(t)$ as $F=mx”(t)$, which means the force on an object is equal to the second derivative of $x(t)$. Recall that we just learned that integrals are the inverse operation of derivatives, so if we want to solve for $x(t)$ in $F=mx”(t)$ we can do it! First we divide both sides by m, in order to isolate the x expression on the right $F/m = x”(t)$. Then apply the integration operation twice in order to undo the two derivative operations.In particular, let us consider the case when $F=\textrm{const.}$ which implies that  then $a(t)=\textrm{const.}=a$. The equation we want to solve is $F/m = a=x”(t)$. Applying the integration operation to both sides of this equation we get $at+C=x'(t)$. By definition $x'(t)=v(t)$ so the constant $C$ can be identified as the initial velocity $v(0)=v_i$. Applying the integration operation to both sides a second time gives us $\frac{1}{2}at^2 + v_it + x_i = x(t)$. This is how the UAM equations are derived: $F=ma$ and 2x integration steps.
• Main idea of this book: understand the math + physics is easier than just learning physics by memorizing the equations. With memorization, you would need to remember three equations of motion as separate entities. If you understand derivatives and integrals then you can remember just one equation $a(t)=a$, which is not much to remember since it is in the name UAM.
• We have now seen kinematics in one dimension. But the real world is three dimensional so we need to learn about the math for dealing with objects in 3D.
3. Chapter 3: Vectors.
4. Chapter 4: Now that we know about vectors we can discuss more physics (mechanics).
• Projectile motion. The position of the object is now a vector $\vec{r}(t)=[x(t),y(t)]$. There are two separate sets of kinematics equations. $x(t)$ is UVM (since no forces in the hz direction) while y(t) is UAM ($a_y=-9.81$ due to the force of gravity).
• Introduce dynamics $\vec{F}=m\vec{a}$, i.e. forces cause acceleration. Forces. Force diagrams.
• Momentum.
• Energy.
• Uniform circular motion.
• Angular motion.
• SHM.

The structure in Chapter 2 is the only new thing. After that, Chapter 4 is pretty much a standard course through the mechanics curriculum. So how is Chapter 2 so special, as to be worth blogging about at 2:44 in the morning?

I will tell you in point form, because it is kind of late indeed:

• It connects nicely with the Precalculus chapter. You just learned how to solve equations for 50 pages, and now I am telling you that you can do physics with this equation solving skill. Yey! Math is useful.
• Then we introduce a bit of basic kinematics concepts $x$, $v$, $a$ and the equations of motion. But then we say where did these equations come from (this is kind of a weak point?). To tell you, we must learn Calculus.
• Bam—drette là—we do a mini course on calculus in 5 pages. Integrals with pictures and FTC. Sure it is complicated but the analogy to f and f-inverse should make it go through.
• Then show derivation of $x(t)$ via int( int($F/m$) ). I can use the exact integral formula since students just saw those formulas as pictures 4 pages ago so they can’t say “i don’t know integrals”.
• Having this early exposure to integrals also helps with the work and potential energy section later on in Chapter 4.
• Basically the 5-page mini introduction to integral calculus is sufficient to do calculus-based mechanics course. The sin/cos derivative info and the chain rule required for deriving the SHM is presented in a just-in-time manner (i.e. in the last chapter).

But who am-I to say what is and isn’t a good way to teach. Only the students can tell me.

Update May 2021: I improved the formatting of the equations in the blog post and added links to the current version of the MATH & PHYS book preview.

### First day of classes

The book is not quite done yet. This sucks, as I wanted to get the book content ready (especially the new chapter on Physics) so that I can crete the flyers from that content. Linear algebra is not done either. And my ticket to Singapore is for the 13th of September. Hmm…

Makes me wonder what the best strategy for the coming week is. The main goal is to get the book into student’s hands this semester and let them read and learn from it. I want to judge the interest in the book (will it sell?), but also judge whether the teaching in it is effective (will they pass?). I suppose testing the quality of the content  is more important than testing how well it will sell. I mean print has been my  favourite monetization strategy since the beginning, but it is unlikely to be the winning strategy. Realistically speaking, I think I am much more likely to see sales on Kindle, iBooks and Kobo rather than in lulu-print. Plus I recently learned that they want a 20% cut from the book profits. WTF? I am pretty sure this 20% thing wasn’t there before.

So in the week that I have left, these are the priorities:

1. Website (Preview PDF, give-me-your-email box)
3. Work on corrections & Chapter 2.

So tomorrow is going to be a Django day I guess 😉

### Cory Doctorow on writing for a living

There is an interesting talk about who controls computers http://boingboing.net/2012/08/23/civilwar.html via HN.

At around 51:30, there is an off-topic question from the audience, which leads to an great answer:

Q: What can you say about making a living writing things. Will you advise it?

A: If you want to make a living writing things I would advise you to stop trying, because that is a bit like saying “I want to make a living buying lottery tickets”. Sounds like a If you don’t have a plan B for earning a living, you have the wrong career. Writing is a very very high-risk entrepreneurial venture that almost everyone who tries it fails at. Some people have succeeded using CC and some fraction without using CC, but they are rounding errors against all the people who try to earn a living with writing.

Ouch! I guess he is talking specifically about writing fiction. Textbooks are OK. I mean somebody has to teach people science. So I will keep going despite this advice.

▷▷   M A T H
P H Y S I C S

I am thinking of de-emphasizing  the “minireference” brand for the upcoming release. It just doesn’t tell that the product is an actual textbook-level coverage. Maybe we could have TUTORIALS in the title? “MATH and PHYSICS textbook”. Ok back to work now. 4 days left till launch.