MATLAB: Loop

MATLAB

for n=1:length(theta_o)

AF(n,:)=1/N*(sin(…

end

here please explain AF(n,:) means

Best Answer

The n th row of the matrix variable AF. The colon stands for all indices, and MATLAB indexes by row-then-column. Hence, AF(n,:) means "nth row, all columns".

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MATLAB: Store variables in a for loop

Hi Davide,

You can make the following modification to the code as shown below, which stores all the loop iteration values in the variable aa:

clear all
xo=[1 2 3 4 5 6 7 8];
yo=[-1 -0.5];
r=0.01;
N=10;
theta=2*pi/N*(1:N+1);
th=0.00235;
for j=1:length(yo)
    for i=1:length(xo)
        [xout(:,i), yout(:,j)]=gencircle(xo(i),yo(j),r,theta);
        [xin(:,i), yin(:,j)]=gencircle(xo(i),yo(j),r-th,theta);
    end
end
aa = zeros(size(xout,1),2,length(yo)*length(xo)); % Initialize the variable
tmp = 1;
for j=1:length(yo)
    for i=1:length(xo)
        aa(:,:,tmp)=[xout(:,i),yout(:,j)];
        tmp = tmp+1;
    end
end
% aa will be a variable of size length(xout) x 2 x (loop iterations)
% loop iterations here is equal to the product of length(yo) and length(xo) (implies 16)
% Each iteration value can be accessed by indexing from 3rd dimension,
% implies for example fifth iteration can be accessed with aa(:,:,5)
function [x, y] = gencircle(xo,yo,r,theta)
x=(xo+r*cos(theta))';
y=(yo+r*sin(theta))';
end

Hope this helps.

Regards,

Sriram

MATLAB: Debugging Help – Write a series of filenames

Hi Cameron,

If I try to run the same code, I get the "Subscripted assignment dimension mismatch.". The problem is in the assignment to myfile. The return of the sprintf (for any N) is a character array of length 15 - so one row and fifteen columns. When assigning this to the myfile matrix, the code requires more than just the row, but the columns for which the sprintf result is destined to:

myfile(n,:)=sprintf('data_%06d.dat',q(n));

Here the colon just means "all columns". Try this and see what happens. (Also consider pre-allocating memory for the myfile matrix.)

Geoff

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MATLAB: Store variables in a for loop

MATLAB: Debugging Help – Write a series of filenames

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