??? Index Exceeds Matrix Dimensions (NEW TO MATLAB)

I am trying to make the script read through 12 sheets, then calculate the average of 5 numbers (for all 22 subjects, for all 12 sheets), and then write a 22x48 matrix that contains the averages on a new spreadsheet. When I run through the script, I get the index exceeds matrix dimensions message. I am assuming this means that what I specified is too large for the matrix to be written. How do I fix this issue?

% Read in a loop of all 12 sheets

n = 12;

j = 0;

B = [];

for k = 1:n;

A = xlsread('ABC.xls',k);

% Loop for all 22 subjects

c = 0;

for i = 1:22;

B(i,j+1) = (A(5+c,8) + A(6+c,8) + A(7+c,8) + A(10+c,8) + A(11+c,8))/5

B(i,j+2) = (A(25+c,8) + A(26+c,8) + A(27+c,8) + A(21+c,8) + A(22+c,8))/5

B(i,j+3) = (A(7+c,8) + A(8+c,8) + A(11+c,8) + A(12+c,8) + A(17+c,8))/5

B(i,j+4) = (A(4+c,8) + A(5+c,8) + A(9+c,8) + A(10+c,8) + A(15+c,8))/5

c = c + 32;

end

j = j + 4;

k = k + 1;

end

%Write the matrix into a separate excel spreadsheet

xlswrite('ABC Output.xls',B);

[Jan]

Please read the "Markup help" link to learn how to format your code.

Answer 1

[Geoff]

I would say it's due to the line:

c = c + 32;

The largest row index you have is A(27+c,8). The value of c gets up to '0 + 21*32' = 672 rows. Does A contain at least 672+27 rows? Does A contain at least 8 columns?

Also, don't increment 'k' at the end of the k-loop. It won't do anything, due to the way the for-loop works but it's not a good idea. If you want every second value of k, then loop:

for k = 1:2:n

[Christina]

There are 705 rows (22 subjects x 32 channels + 1 row for headings) and 8 columns. I am trying to get the script to look for specific channels that repeat after set of 32.

Answer 2

[Jan]

It is useless and confusing to increase the loop counter inside the loop:

for k = 1:n;
  ...
  k = k + 1;   % <- omit this line
end

The best method to solve such problems is the debugger. Type this:

dbstop if error

in the command line (or use the debug menu in the editor accordingly). Then start your program. If an error occurs, Matlab stops and you can inspect the values of the variables in the command window.