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Integration using matlab

by Execute
Tags: integration, matlab
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Execute
#1
Mar25-08, 07:46 AM
P: 2
Hi everyone, I have a problem in finding an integral of a function. I'm given the following function: x(t) = t + 1 (-1 <= t < o ); e^-t (0<= t <= 2); 0 (otherwise).I have to find the integral and plot it with its derivative and the given function.

Here is my code:
%Set up integral vector
u(1:1000) = 0;
%Find the integral
for n = 1:999;
if( (t(n)>= -1) & (t(n)<0) );
u(n) = 0.5.*(t.^2) + t;
end
if ( (t(n)>=0) & (t(n)<2) );
u(n) = -1.*(exp(-t));
end
if( (t(n)>2 ) )
u(n) = 1.*t;
end
end
subplot(3,1,3);
plot(t,u);

I get the following error when trying to run the code:
??? In an assignment A(I) = B, the number of elements in B and
I must be the same.

Error in ==> tut1 at 32
u(n) = 0.5.*(t.^2) + t;
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LeBrad
#2
Mar26-08, 08:18 AM
LeBrad's Avatar
P: 212
Quote Quote by Execute View Post
Error in ==> tut1 at 32
u(n) = 0.5.*(t.^2) + t;
In these three lines
     u(n) = 0.5.*(t.^2) + t;
      u(n) = -1.*(exp(-t));
      u(n) = 1.*t;
you are trying to store a vector in a scalar's place. u(n) is a scalar and t is a vector, so change t to t(n) and you will be fine. Also, be sure to define t properly (don't see it in your code), e.g. t = linspace(-1,2,1000).
ekeenz87
#3
Apr6-11, 10:17 PM
P: 1
i have 1 question
how do i apply 1/s in simulink block to M-code,
for example
Xdot to X
in simulink, we just apply the 1/s(integration block).
so i just want to know, is it possible to integrate the Xdot to X in m code??


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