MATLAB Answers

Tom
0

For loop - what about my min and max values?

Asked by Tom
on 11 Dec 2011
For loop - what about my min and max values? I'm using a for loop and although my plot is right, I'm only seeing my maximum x-axis value in the Workspace Max column. Is there a way to have the Min and Max columns actually correct?
Many thanks
iter=1;
for f=50:1000
rho_a=1.2041;
sigma=11000;
phi=0.99;
alpha=1;
c=343.26;
i=sqrt(-1);
L=0.1;
a=0.03;
k_a=(2*pi*f)/c;
k_2=((2*pi*f)/c)*sqrt(alpha-((i*sigma*phi)/(2*pi*f*rho_a)));
z_c_2=((rho_a*c)/phi)*sqrt(alpha-((i*sigma*phi)/(2*pi*f*rho_a)));
z_1=(z_c_2*cot(k_2*L)*(cos(k_a*a)+(i/(rho_a*c))*sin(k_a*a)))/(i*cos(k_a*a)-(1/(rho_a*c))*sin(k_a*a));
R=((z_1/(rho_a*c))-1)/(1+(z_1/(rho_a*c)));
Rrec(iter)=R;
AbsCoef=1-(real(R))^2;
AbsCoefrec(iter)=AbsCoef;
z_1rec(iter)=z_1;
iter=iter+1;
end
plot(50:1000,AbsCoefrec)

  2 Comments

Jan
on 11 Dec 2011
What is "the maximum x-axis value" and what is the "Workspace Max column"? And how is the correctness of the "Min and Max columns" defined? What the is the relation between the question and the code?
To improve the code (dramatically!) look in this forum for the term "pre-allocation".
i is already defined in Matlab - as long as you haven't redefined it earlier in the program you don't need to do i = sqrt(-1)

Sign in to comment.

1 Answer

Answer by bym
on 11 Dec 2011
 Accepted Answer

Your x axis is the loop variable f, which can only take on one value at a time, thus the min and max are the same. To do what you want, you would have to modify your code something like this
freq = 50:1000;
AbsCoefrec = zeros(size(freq)); % preallocate!
for f = freq
% ---insert code here---
end
plot(freq,AbsCoefrec)

  1 Comment

Tom
on 11 Dec 2011
right okay. is req the same as rec?
many thanks for that

Sign in to comment.