How to solve "Attempted to access index 12 of an array with smaller dimension sizes" problem?

Hi. I get an error "Attempted to access index 12 of an array with smaller dimension sizes".

This error occurred when I change 'constant block' with 'from file block'.

In the constant block, I have a set of data like this...

[35.85
35.74
36.03
35.36
35.36
35.74
36.03
35.95
36.03
35.82
35.83
35.25
35.9
36.07
36.2
35.92
35.66
35.94
36.02
35.94
35.92
35.84
36.2
36.28
]

and in the from file block the data is just the same as the data above.

Here is my code in the MATLAB function block.

 function Consistency  = detection(x)
    H = x;
    S = std(H(12:24,:));
    Consistency = S;
  end

Please give your suggestion.

Thank you.

[Walter Roberson]

Please confirm that in the file that you are getting the data from, that the data is a column vector, not a row vector. Also please check the signal properties to ensure that it has not become a row vector.

Is it possible that you will ever use the block with multiple columns of data? If not then use std(H(12:24)) instead

Also, since std() is a MATLAB function call, before that line you should have

S = zeros(1, size(x,2));

This will tell the code generator to copy the result of the function back into memory once the call is made (otherwise you will get an error about mxArray that you would have difficulty understanding.)

[SyukriY]

I actually just want to calculate the data from row 12 to 24. What should I do?

[Walter Roberson]

function Consistency  = detection(x)
  assert(size(x,1) >= 24);
  H = x;
  S = zeros(1, size(x,2));
  S = std(H(12:24,:));
  Consistency = S;
end

If the assert() fails then the problem would be that you did not have at least 24 rows.

[SyukriY]

Hi, Walter Roberson.

As you assume, the assert fails. But, I have 24rows in the file. What could be wronged?

Answer 1

[Preethi]

Hi,

Save the data in .mat as columns, use transpose at the start of function.

The file must contain a matrix of two or more rows. The first row must contain monotonically increasing time points. Other rows contain data points that correspond to the time point in that column. The matrix is expected to have this form.
<http://www-rohan.sdsu.edu/doc/matlab/toolbox/simulink/slref/fromfile.html>

[SyukriY]

Thank you for the solution. But can you explain it more, cause I don't get it?

Maybe some picture can give me more understanding. Besides, I think the file has no issue. The file is in .mat format.

Maybe you can look at Walter Roberson suggestion. Until now I'm stuck in this problem.

[Preethi]

hi,

'From file' block reads first row as time stamp and the data in other rows as values corresponding to that time stamp. in your case the output of the block will contain only two samples of data, hence the error. Just transpose the data and save again in .mat file, it will 2 x 24.

Inside your code use x =x.' as first line and then check.

[SyukriY]

Yeah, got it.

Thank you so much for your help.

Answer 2

[Walter Roberson]

When you use From Workspace to bring in a matrix (I have not tested From File as much):

Rows of the variable correspond to timepoints. Column 1 will be used for the corresponding time. For each timepoint, a row without the first column will be passed to the function, but the row will be passed as a column vector. For example, for a 25 x 30 matrix, since the first row is time, there are 25 x 29 remaining data, and each function call will be passed a column of 29 values, with the function being called multiple times.

If you are trying to do this at initialization time, a one-time calculation with all of the data in the matrix, with the output becoming more or less a parameter for the run, then I am not sure if that is possible, but I would not rule it out (I do not have the experience to say.)

[SyukriY]

Thanks to you too...