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Proposal: Linear Algebra Study Group
54 points by gruseom on Sept 13, 2011 | hide | past | web | favorite | 62 comments
Inspired by http://news.ycombinator.com/item?id=2992963, let's start a group to (re-)learn linear algebra.

Who's in, and how shall we go about it? Something like a chapter every week or two, plus do the exercises?

Time to trade in a few hours of internet downtime and actually learn something.

Edit: here's what seems to be emerging. We'll read Strang's "Linear Algebra and its Applications" (ISBN 0030105676), one chapter every two weeks plus exercises. We'll stay here where the community is, unless proven otherwise. And... that's about it! I like systems with few rules.

The one sticking point is waiting for people to get the book. Anyone who, like me, just ordered a cheap copy on Abebooks (probably a re-import from India) is going to be blocked for a bit. I will post again when my copy arrives, and will email everyone who (a) has said on this page that they're in and (b) has an email address in their HN profile. Will that be suitable?

I'll check back this evening.

Chapter ever two weeks plus exercises sounds simple, doable, reasonable. Let's do it that way.

Once we feel like we've picked our book, let's decide on a date to start; 2 weeks from that date, one of us will just post a "STUDY HN:" post for the first chapter.

We can figure out the formalities, like, what do those threads look like, once we get started. :)

I'm in. How do we coordinate? http://convore.com perhaps?

I seriously think we could just do it on HN threads...

There are feature-y-er places to do it, but this place actually works.

I agree. I'm superstitious about origins. When something spontaneously happens at location X it's good to let it continue to evolve there. I say we stay where the party started. We can post occasionally and nobody who's uninterested need look at it. I also confess to tasting sweet irony in the idea of turning HN to more productive use. I feel like I've finally got my enemy in a corner. (The internet has never stopped me from working, but man has it stopped me from learning. But I digress.)

As for what book: "Linear Algebra and its Applications" by Strang does sound like a good fit for hackers. I was convinced by this review: http://www.amazon.com/review/R289C7K1TN2RO2/ref=cm_cr_pr_per.... Some cheaper copies are available on Abebooks.

There's a case to be made for the other Strang, but again - origins are magic, so unless there's a compelling negative I say we stick with tptacek's original inspiration.

How many times have I seen an ad hoc thread that people would just hit reply-all to converted into a mailing list. Instant community killer.

All of that sounds good—count me in.

Should we wait a week before starting so people can get their hands on the text?

I'm in. Got the 3rd ed. while waiting for the shipment of the 4th (possibly long wait). Let me know if you're in a similar situation.

So do we post our answers and get downvoted if wrong? (and sometimes anyway)

It's hard to beat an elegant site like this that we're already registered for, but I'm having trouble visualizing matrices in this markup.

  [ 1 0 0 ]
  [ 0 1 0 ]
  [ 0 0 1 ]
OK, worth a shot.

It may be good to hide solutions behind a pastebin link, rather than directly including them in a comment & spoiling things.

I'd think we'd mostly be saying "I liked this" or "I didn't understand that", not so much quizzing. But I don't know, never done this before.

Can always link pictures to threads if ASCII gets too hard.

As long as we don’t need to use MathML. I can’t spare an hour and a half to construct each post.

I think old threads get locked (can't post new comments) relatively quickly on HN which would make it tough, it would involve making new posts and expecting everyone to find the new one. (Feel free to correct me on the locking thing)

Once in a blue moon I go back and find hanging replies to my comments, so I'm pretty sure these things stay alive for weeks, which is as long as we'd need them to.

Works for me. Book acquired.

Convore wouldn't be a bad idea for coordination and meeting. How about it ?

I think this is a great idea, although I don't know if I'm a good candidate for it, since I never officially got past a Pre-Calculus level.

I recently decided in the past couple weeks to go through Khan Academy from the very beginning (simple arithmetic! :), and run through every one of their exercises. I'm moving pretty fast through all the refresher courses, and I'm amazed at what I've retained (and disappointed at what I've lost).

I've completed 113 out of 171 exercises in my off hours in the past couple weeks, and once I've gotten through them all, I'm going to run through MIT 18.01 Single Variable Calculus, 18.02 Multi-Variable Calculus, and 18.03 Differential Equations.

From there, I was planning on doing MIT 18.06 Linear Algebra, so even though I don't think it would work out for me to jump in to a group like this without the proper background, I'll be following the progress of things closely.

In fact, the idea of HN being a platform for self-directed group education is a brilliant one. While there are already websites focused on that, I know we're all impressed enough by the HN readership that there is an obvious advantage of organizing it here. Hopefully this experiment can work for other areas of study as well.

For the most part, I don't even think you need 18.01. 02 or 03.

there may be a few applications in 18.06 that you miss out on but it wont' be a big deal.

Interested; please include me. Once the book arrives I'll have to confirm I can make the time.

In terms of how: I was part of a terrific, useful "HN reads SICP" group a while back (http://news.ycombinator.com/item?id=428248, couple of us made it through to the end). In that case the meeting place was simple (irc) and we generally linked to our answers on pastebin/github/personal site which supported whichever features we needed it to. An HN thread per "meeting" could work similarly as a hub.

It is probably useful for each person to chime in separately, e.g. "I agree that this is the right answer" or "I also have this confusion", despite this not being ordinary HN etiquette. That allows us to know how many people are participating and evaluating answers, which is difficult, especially given hidden comment points.

It would be best to do this somewhere that supports MathJax (http://www.mathjax.org/). HN does not, which could make it awkward to discuss math in an HN thread.

There are three reasonable ways to add MathJax support to a site.

1. Get the site owner to do it. The site owner simply has to toss in a script tag that loads MathJax from the MathJax CDN and sets some configuration options. Someone would need to convince PG that this is worthwhile. (I've done some timing tests, and MathJax doesn't seen to cause any noticeable performance problems when used on pages that contain no math. Any decent browser caches the script so load time of the script is not a problem).

2. The user can use a Greasemonkey script to load it, for browses that support Greasemonkey scripts. Here's an example that loads MathJax on Reddit: http://userscripts.org/scripts/review/108770. This could trivially be modified to work on HN instead of Reddit.

3. Safari doesn't support Greasemonkey scripts. There is a Safari plugin to add that functionality, but it does not work very well. I wrote a Safari extension to load MathJax (or Tex The World, discussed below) on Reddit: https://github.com/tzs/Reddit-Math-Display-for-Safari. This could easily be modified to work on HN instead of Reddit.

On Reddit, in /r/math, the convention is to use LaTeX delimited by [; and ;] to mark math, and to use a script called Tex The World to render it (http://thewe.net/tex/). That script finds the math, and sends it off to CodeCogs.com where it is rendered and an image is returned for display. This occasionally causes problems due to the load on CodeCogs.

To work around this, someone has a hacked version of the that script (link available in the sidebar on /r/math) that uses the Google Chart API to render small equations and does some kind of caching.

I'd recommend NOT using either of these. The author of TeX The World stopped work on it quite a while ago. There's no licensing information on the site so it is not clear if anyone else can take it over, and by using an external service to render the math it is fragile.

MathJax seems to be the best approach. That's what they are using at mathoverlow and math.stackexchange.com. Note that if MathJax is loaded by the page itself, rather than by an extension, then it works great on iOS and most other major mobile web devices, in addition to pretty much all major desktop browsers, without the need for the end user to do anything special.

Testing new HN version of script: [;A\boldsymbol{x}=\lambda\boldsymbol{x};]

Seems to be working, in Chrome at least. Can some other people try it out? http://userscripts.org/scripts/show/112966

Put latex code inside square bracket semicolon pairs: [;...code...;]

Note that /r/math on Reddit is using those delimiters because that's what Tex The World uses. I don't see any particular reason to use those over just sticking with the MathJax defaults, which are backslash-brackets and dollar dollar for display math, and backslash-parens for inline math.

For your script, this can be achieved simply by deleting the line in the configuration that sets the inline math delimiters.

I've tested, and the default delimiters seem to work fine on HN.

Cool, thanks. That would be better.

Testing new version: \(\sum_{i=1}^n c_i \phi(\|\boldsymbol{x}-\boldsymbol{x}_i\|)\)

Now updated and tested successfully in Chrome and Firefox (multiple versions of each) on Linux and Windows, with http or https.

Not working in Tampermonkey on Android (the script runs, but the notation doesn't happen).

Now using standard MathJax delimeters, \(...code...\) for inline or \[...code...\] for an equation.

Works for me on Chrome 14.

Testing: [;\frac{du}{dt};] [;\left[ \begin{array}{cc} 1 & 0 \\ 0 & 1 \end{array} \right];]

Now changed to use the MathJax default delimeters, as tzs explains.

How about OpenStudy studygroup for MIT linear algebra course? http://openstudy.com/groups/mit+18.06+linear+algebra%2C+spri...

I'm interested, except I recently bought his _Introduction to Linear Algebra_ (to go with his opencourseware). I'll probably eavesdrop and do the exercises in that one instead.

Yeah, that's the argument in favor of the other Strang: it's more standard and would allow piggy-backing on the open course. Still, the material is mostly going to overlap.

> Time to trade in a few hours of internet > downtime and actually learn something.


Some tools I can recommend are dokuwiki with jsMath plugin and etherpad for live collaboration/note-taking

http://piratepad.net/sj8l1FIUIK --> I started one pad for this project.

If someone is willing to setup a public dokuwiki on their server, I can provide examples of latex code for matrices and vectors.

Which textbook are we talking about? Timing isn't perfect for me, but I'm willing to at least try until everything catches up with me.

I'd also like to know which book. I just bought Strang's Introduction to Linear Algebra to study along with his video lectures.

If it's based on this book I'd love to join.

Already mentioned, but if you really like using a textbook I can't recommend Strang's book enough. Its awesome, and go really well with his lectures.

Count me in. I already have Strang's textbook and have watched some of his lectures.

However, I was quite impressed with a few minutes of Khan Academy I watched the other day. I don't know what the dependency chain is for their L.A. modules but that site seems to have some good metadata and group organization tools.

I've been liking Khan's linear algebra stuff too, but feel like its time to level up.

I'd like to be involved (email in profile).

Are there significant differences between editions? For those not employed by Thomas, the 4th edition is a expensive book even when used. The 3rd, by contrast, has many affordable used copies available. And are the international versions identical?

Same thinking. $90 used is just too much, so I picked up the 3.ed. Hopefully it's good enough. Yes, please count me in too!

It seems one can get the International Edition of the 4th edition from Abe Books at a greatly reduced price:


I'm in. Does it matter which edition we use?

As for notation and sharing images, this is a great tool... provided you know LaTeX (which is worth learning anyway):


Would definitely be interested in this. Use it everyday for stats, but would like to get better at the fundamentals.

I think for it to be most efficient, we should use the book that coincides w/ the MIT lectures.

I'm in for this. A chapter every 2 weeks sounds like a good pace without any unnecessary pressure. How do we coordinate? @gruseom, would you like to take the lead?

I am in! I live very far from Amazon.com and I don't have Kindle. Is there a place to source the book's pdf version?

I'm in; I have the book; Is the next checkpoint on Sep 27 (Chapter 1)?

With 8 chapters, this will stretch past Dec, is this correct?

That sounds good to me. Here in Chicago? If we need a location, my office and apartment building are options...

Daniel's in Canadia. We can just do it on HN, with a post every other week. It probably won't hit the front page often, but who cares?

We were going to do this internally at our Chicago office (Timur is a math grad student), so I'm open to Chicago-specific extensions, especially if they involve alcohol. I'm better at math when slightly buzzed.

Agreed. Alcohol & Chicago-extendsion - I'm in for that.

I would be curious to do this and am in Chicago. Hopefully I wouldn't hold back the group!

I'm in. Though I don't think HN is the place to run the study group.

I'm in. My email is in my profile and is loganfrederick@gmail.com

I'll get on board; I need to relearn this. Email in profile.

I'm interested! please find my email in my profile.

Awesome idea, I'm in. Time to go get Strang...

I'm in. I have the 3rd edition of this book

I'm interested in participating.

I'm game. Where do we sign up ?

You don't. That's the best thing about it. We'll agree on this thread what book we're using and when the first study thread will happen; then, a couple weeks from now when it's time, someone will just post STUDY HN: Linear Algebra Chapter 1, and I will ask some dumb question and Colin Percival will jump on me for being dumb and we'll be off to the races.

I'm psyched.

if you're relearning, you should use Horn and Johnson's Matrix Analysis IMO

I'd like to join this.

I'm in. There is a free linear algebra text from UPS (U Puget Sound) as well.

I'm in, probably.

Yesterday I pushed a tiny javascript algebra on github. I'll just leave the link here: https://github.com/plainas/ualgebra.js

It might be useful for you guys to check solutions and such.

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