??? Improper assignment with rectangular empty matrix.

I'm doing my report. Matlab is used to solve the question. My code like this:

function y=STFT(x,seg,step);

[Lx chan]=size(x);

maxi=(Lx-seg)/step;

for i=1:maxi;

X=x(1+(i-1)*step:seg+(i-1));

Z= X*step;

f=fft(Z);

P=f.*conj(f);

y(:,i)=P;

end

However, it show error exist at "y(:,i)=P; ". May i know how to solve it?

Besides that, is that other formula can i replace "X=x(1+(i-1)*step:seg+(i-1));"?

Hope can get the answer by today as my code have to submit tomorrow.

Thank you.

Answer 1

[David Young]

I suspect your problem is that this line:

X=x(1+(i-1)*step:seg+(i-1));

should read

X=x(1+(i-1):step:seg+(i-1));

[Goh]

but matlab there show error at y(:,i)=P. Why is it??

[David Young]

If the size of X is computed incorrectly, that could cause an assignment error when you try to assign P to a column of y.

[Goh]

i see. For the line

"X=x(1+(i-1)*step:seg+(i-1));

Z= X*step;"

is that got other way to write this formula?? Because what i posted is sample answer from lecturer, we need to change it. Any idea?

[David Young]

It depends what the code is intended to do. It's hard to fix code without having a specification for the computation - more details of what you are aiming at would help.

By the way, I see that in your comment you show your original line of code, not my correction. Is that because the correction does not work?