Unable to perform assignment because the indices on the left side are not compatible with the size of the right side. What does this mean?

Question

Error in segment(n_start)=data(n_start:(n_start+ window_size-1));

%% input data matrix
DDD=load('data2.mat');
data=DDD.data;
N_max=length(data);
window_size=256*3; %% 256 for 1 second ==> 3 seconds
step_win=128*3; %% overlapping window ...by 50%
segment=zeros(4798,768);
count=0;
for n_start = 1:step_win:(N_max-window_size)
    count=count+1;
    segment(n_start)=data(n_start:(n_start+ window_size-1));
end
plot(Segment)
xlabel('time')
grid on;
title('data of channel1');

You don't say where you got the error (always include the entire error message), but I assume it's on the line assigning Segment(n_start) where you're trying to fit a 768-element vector into a single array element. I don't think that's what you want to do. Also, you should check your variable names. You initialize segment but assign Segment. Those are not the same. — beaker
I want the array segment=zeros(4798,768) to be filled each time the loop iterate — gehan

Mefitico Mefitico · Accepted Answer · 2019-10-15T19:00:24

In the passage:

segment(n_start)=data(n_start:(n_start+ window_size-1));

You are attempting to attribute a vector into a 1x1 matrix.

If segment is a vector, then segment(n_start) is its value at the location n_start, if n_start in an integer, then segment(n_start) is 1x1.

On the other hand n_start:(n_start+ window_size-1) is a vector that spans from n_start and increases one by one until (n_start+ window_size-1). And that due to how the : operator works. Because window_size=256*3, then it is a 767-long vector.

When you call data(n_start:(n_start+ window_size-1)), you are asking all the values of data in the indexes contained in the vector n_start:(n_start+ window_size-1).

Hence, in the error line, you trying to atribute a vector of size 767x1 to a 1x1 matrix. that is why it doesn't work.

Unable to perform assignment because the indices on the left side are not compatible with the size of the right side. What does this mean?

1 Answers