

Proposal: Linear Algebra Study Group - gruseom

Inspired by http://news.ycombinator.com/item?id=2992963, let's start a group to (re-)learn linear algebra.<p>Who's in, and how shall we go about it? Something like a chapter every week or two, plus do the exercises?<p>Time to trade in a few hours of internet downtime and actually learn something.<p>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.<p>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?<p>I'll check back this evening.
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tzs
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.

~~~
mkl
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...;_ _]_

~~~
tzs
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.

~~~
mkl
Cool, thanks. That would be better.

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

------
tptacek
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. :)

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

~~~
tptacek
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.

~~~
gruseom
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...](http://www.amazon.com/review/R289C7K1TN2RO2/ref=cm_cr_pr_perm?ie=UTF8&ASIN=0030105676).
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.

~~~
akkartik
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.

------
michaelchisari
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.

~~~
asdf333
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.

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aamar
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.

------
timgluz
How about OpenStudy studygroup for MIT linear algebra course?
[http://openstudy.com/groups/mit+18.06+linear+algebra%2C+spri...](http://openstudy.com/groups/mit+18.06+linear+algebra%2C+spring+2010)

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

Amen!

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.

------
silentbicycle
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.

~~~
gruseom
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.

------
endian
I'm in!

By the way, some less applied materials include:

\- [http://www.amazon.com/Linear-Algebra-Right-Sheldon-
Axler/dp/...](http://www.amazon.com/Linear-Algebra-Right-Sheldon-
Axler/dp/0387982582)

\-
[http://www.math.mcgill.ca/goren/AlgebraII07-08/CourseNotesMa...](http://www.math.mcgill.ca/goren/AlgebraII07-08/CourseNotesMath251.pdf)

------
bugsbunnyak
Two collaboration suggestions:

Sage: <http://sagemath.org/>

<http://math.chapman.edu/~jipsen/tiddly/tiddlymath.html> (related example:
<http://deferentialgeometry.org/>)

------
ebiester
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.

~~~
corey
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.

------
marshray
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.

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

------
nkurz
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?

~~~
fuzzythinker
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!

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

[http://www.abebooks.com/servlet/SearchResults?isbn=003010567...](http://www.abebooks.com/servlet/SearchResults?isbn=0030105676&sts=t&x=0&y=0)

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biofox
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):

<http://www.codecogs.com/latex/eqneditor.php>

------
trenthauck
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.

------
tsycho
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?

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dthakur
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?

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ejanus
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?

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

~~~
tptacek
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.

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

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

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

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

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

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

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

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ecruz3
I'm interested in participating.

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jcarden
I'm game. Where do we sign up ?

~~~
tptacek
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.

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

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mavelikara
I'd like to join this.

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

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mkl
I'm in, probably.

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skeptical
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.

