Is there any special rules for nesting if-statement in for-loop in MATLAB? - matlab

Question

I am trying to create a signal and then build a discrete-time signal by sampling the CT signal I create first. Until the last for-loop, things work out fine but I need to take N samples seperated by T. Without an if statement, I am getting an index out-of-bounds error and I had to limit sampling within the duration of the signal. For some reason, my code goes into if statement once and no more, and for debugging, I am printing out the values both in if and out of if. Although the logical operation should be true for more than one iteration(printing statements will show the values), it just does not print the statements inside the if-statement. What's wrong here?
function x = myA2D(b,w,p,T,N)
%MYA2D description: Takes in parameters to construct the CT-sampled DT signal
%b,w,p are Mx1 vectors and it returns Nx1 vector.
timeSpace = 0:0.001:3*pi;
xConstT = zeros(size(timeSpace));
%Construct Xc(t) signal
for k = 1:size(b,1)
temp = b(k) .* cos(w(k).*timeSpace + p(k));
xConstT = xConstT + temp;
end
plot(xConstT);
%Sampling CT-Signal to build DT-signal
disp(strcat('xConstT size',int2str(size(xConstT))));**strong text**
x = zeros(N,1);
sizeConstT = size(xConstT);
for i = 0:N-1
index = i .* T .* 1000 + 1;
disp(strcat('indexoo=',int2str(index)));
disp(strcat('xConstSizeeee',int2str(sizeConstT)));
if index <= sizeConstT
disp(strcat('idx=',int2str(index)));
disp(strcat('xSize',int2str(sizeConstT)));
%x(i+1,1) = xConstT(index);
end
end
end

Answer 1

sizeConstT = size(xConstT); creates an 1x2 array so you compare a float to an array, and your code enters the if loop only if comparison to each element of the array is successful. This example illustrates the issue:
if 1 <= [1 12]; disp('one'); end % <- prints 'one'
if 2 <= [1 12]; disp('two'); end % <- prints nothing
Your code will work with sizeConstT = length(xConstT);