MATLAB Answers

## For loop and indexing combined?

Asked by Tom

### Tom (view profile)

on 10 Jan 2012
Accepted Answer by Walter Roberson

### Walter Roberson (view profile)

I think I'm nearly there with this code.
close all;
clear all;
l=0.33;R=100;T=68;m=0.000125;w0=0.1;t=0;mu=m/l;c=sqrt(T/mu);r=2;x0=l/r;
x=linspace(0,0.33,10)
iter=1;
for n=1:5000;
wxt=((4*w0)/pi)*exp(-R*t)*((l/(pi*n^2*x0))*sin((n*pi*x0)/l))*sin((n*pi*x(1))/l)*cos((c*n*pi*t)/l);
wxtrec(n)=wxt;
iter=iter+1;
end
w=sum(wxtrec)
What I actually want is for the code to repeat for each value of x - instead of just for the first indexed value - x(1) - as it is now.
Right now, w, is correct for x(1). Is it possible to set up a new outer for loop, which uses subsequent values of x ie. x(1), x(2) etc. instead of just using x=1,2,3,4..?

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## 2 Answers ### Walter Roberson (view profile)

Answer by Walter Roberson

### Walter Roberson (view profile)

on 10 Jan 2012
Accepted Answer

Yes, you had a suitable nested loop in one of your previous versions of this code.
Note: you never use iter so you might as well get rid of it.

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Answer by Tom

### Tom (view profile)

on 10 Jan 2012

Okay - I've not come across a few of these things before. I hope you don't mind if just fire off a few questions about it.
What does the .' do aster n=(1:5000)? Why the p1 and p2? What is bsxfun? and @times?
On a different note, Mathematica has the ability to make a graph which will play in real time - so you can have an extra variable - time, t maybe. Does Matlab have anything similar? At the moment I'm looking at either doing a series of graphs for progressive values of time, t or trying a surf graph.
Many thanks, Tom

Walter Roberson

### Walter Roberson (view profile)

on 10 Jan 2012
The .' is transpose, converting the row vector (1:5000) in to a column vector.
bsxfun is the Binary Scalar Expansion Function routine; see your documentation.
@times is a function handle to the built-in element-by-element multiplication routine more commonly known as .*
For animation, please see http://www.mathworks.com/help/techdoc/creating_plots/f10-1460.html

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