Matlab-Intro-MIT-IAP-2008 Google Group

Class is now over.

farj...@gmail.com (Yossi) — Thu, 31 Jan 2008 20:18:53 UT

Hi all,

I'm a little disappointed by the weak show of people today...The
project is the part where you would have learned the most in this
class. By not doing the project, you are committing yourself to
forgetting most of the material. You need to strike the metal while it
is hot...But there's still hope! Finish your project over the weekend

Feedback on Intro to Matlab 2008 (Yossi Farjoun)

farj...@gmail.com (Yossi) — Wed, 30 Jan 2008 18:11:17 UT

Hi all.

In order to create a better departmental offering, and to get feedback
on my teaching, I ask that you take a few minutes to answer the
following questions. In order to guarantee you express your true
thoughts about me and the class please email your reply to
w...@math.mit.edu (the undergraduate office). Make sure you do not

Re: Question about today's exercise

yfarj...@math.mit.edu (Yossi Farjoun) — Fri, 25 Jan 2008 13:00:29 UT

Masaharu,
The third way you suggested is one way I was thinking about (note that you
can change the 5 to a 100 and it will create a 100x100 matrix...)
but you can also do
a=[1:5]'
r=a(:,ones(1,5))
The fourth way you did has a colon between two vectors...I'm not sure what
you expect that to do.
cheers,

Re: Question about today's exercise

masaharu.aiu...@sloan.mit.edu (Masaharu Aiuchi) — Fri, 25 Jan 2008 19:56:40 UT

Thanks for your reply.
is a quite interesting way. This trick looks a bit similar to ' for i
= [ ones(1,5) ] ' in respect that a kind of iterator is proceeding
from 1 to anther 1, right ? Now I understood how it is going in Matlab.
Have a good trip.
Masaharu

View this page "Lecture 6 Notes"

smpg...@gmail.com (rumela@mit.edu) — Thu, 24 Jan 2008 19:20:27 UT

Lecture 6 notes are published in case you wanted them...:-)

Click on [link]
- or copy & paste it into your browser's address bar if that doesn't
work.

Lecture 6 write-up

farj...@gmail.com (Yossi) — Thu, 24 Jan 2008 14:41:26 UT

Hi all.

I'm leaving for the weekend right after class today, and thus will not
have the time to write up my lecture summary.

I would greatly appreciate if a few of you could collaborate on
writing up the notes.

You can simply click on "Pages", and then on "new page", and type
away. you can edit a previously edited page (kind-of like a wiki), or

Re: counter

farj...@gmail.com (Yossi) — Thu, 24 Jan 2008 04:45:12 UT

Nice code.

2 comments.

1. You have an empty line as the first line of the code. the very
first line must have the "function y = ...." code, or a comment
(starting with %)
no empty lines allowed before the keyword function...This might be
your only problem.
2. you can put the y=counter1-1 outside the while loop. no need to

counter

farj...@gmail.com (yossi farjoun) — Thu, 24 Jan 2008 04:42:18 UT

Hi Yossi,
I have attached my version of the last-ish problem for lecture 5. I can't
seem to get it to work. What would you suggest?
function y = counter(x)
counter1=1;
while x>1
counter1=counter1 + 1;
if mod(x,2)==0
x=x/2;
else
x=3*x+1;
end

Re: Lect 5 exercise -20000th Fibonacci number

farj...@gmail.com (Yossi) — Thu, 24 Jan 2008 03:15:16 UT

GOOD POINT!

I wasn't thinking when I gave you that exercise...it does indeed grow
to be too big for matlab. So let's find the 100th Fibbonacci number
instead...(I'll change the exercise)

Yossi.

Lect 5 exercise -20000th Fibonacci number

farj...@gmail.com (yossi farjoun) — Thu, 24 Jan 2008 03:12:35 UT

Hi Yossi,
I was doing the exercise, and it seems to be working, except the value for
the 20,000th number comes out as Inf. I tried changing the format of the
number, but it didn't help. Is there a way to see the value of the number
or is it just Inf?
Thanks,
Jessica

Re: help: lecture 4 question 2

farj...@gmail.com (Yossi) — Wed, 23 Jan 2008 20:16:42 UT

Dear M,

There are several things that need to be corrected in your code:

1. (line 2) 1:10^(-6) is an empty vector. be careful with operator
precedence.
2. (line 3) even if that was a vector, it would only be a vector of
size 10...and in the loop, n would just be a single number...not what
you wanted I think. Perhaps you need another variable...just like my

help: lecture 4 question 2

farj...@gmail.com (yossi farjoun) — Wed, 23 Jan 2008 20:05:27 UT

Hello,
I have problems solving the second questions on lecture 4, warm up:
Find a value of N so that the sum is close to pi/4 (with difference < 10^-6)
I have written the following code:
counter=0;
for n=1:10^(-6)
a=(1).^(n+1)./(2.*n-1);
sum(a);
counter;
if
sun(a)-(pi/4)<10^(-6);
break

Re: sprintf lec4

farj...@gmail.com (Yossi) — Wed, 23 Jan 2008 20:01:04 UT

Shammi,

great questions.

s is a "format string" when used as the first argument of fprintf or
sprintf it tells the function how to generate the result (sprintf
returns the result, while fprintf write the result to the screen, or a
file)

in the format string, you can have "place holders" for other input. so

sprintf lec4

sha...@mit.edu (Shammi S Quddus) — Wed, 23 Jan 2008 06:13:18 UT

I was running this if loop from your lecture notes

x = rand;

s = 'The number %g is %s than 0.5\n';

if x<0.5

fprintf(s,x,'less')

else

fprintf(s,x,'more')

end

questions: what does the %g and %s represent? what does it say in
english? also are the alphabets random or each signify a different

Re: syntax on summing

farj...@gmail.com (Yossi) — Tue, 22 Jan 2008 19:49:36 UT

Hello,

I may have already answered you in class, but in any case, I'll answer
the list. The division needs to be pointwise. so use ./ instead of /

cheers,

Yossi.