Error in reading dimensions of a .mat file

q is a matrix of 1*96. f_s is a matrix of 7*1. I am getting an error saying : index exceeds matrix dimensions.

And also the maximum value i = 1 and j=46 and e_dist matrix obtained is a 1*46 matrix. Expected values of i=7, j=96 and e_dist should be a 7*96 matrix.

 f_s = 'C:\Users\Toshiba\Desktop\friday work\';

q = 'C:\Users\Toshiba\Desktop\friday work\1_1_2.mat';

s = dir(f_s);

s([s.isdir]) = [];

e_dist=[ ];

for i=1:1:size(s,1)
  word=strcat(f_s, s(i).name);
    for j=1:1:size(q,2);
       e_dist(i,j)= sqrt(sum((word(i,j)-q(j)).^2));
    end

end

Answer 1

[Walter Roberson]

Your line

word=strcat(f_s, s(i).name);

creates "word" as a string, which is a row vector of characters. But then your line

e_dist(i,j)= sqrt(sum((word(i,j)-q(j)).^2))

attempts to access the i'th row of that character array; when "i" reaches 2, there will not be a 2nd row of the string and so you will get index exceeding matrix dimension.

Your "q" is not a matrix of 1*96: it is a character vector of 1*46 or so. Your "f_s" is not a matrix of 7*1: it is a character vector of 1*37 or so.

Your line

e_dist(i,j)= sqrt(sum((word(i,j)-q(j)).^2))

is calculating the Euclidean distance between file names.

It appears you have confused file names with the contents of the file.

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[divya r]

I have extracted the features from a lot of images n stored it as row vectors in individual mat files. I am using euclidean distance method to find distance between each of them.

I have seen some programs which are working perfectly fine using the method i have used above. I dont understand why it isnt working here.

Should i not convert it into string? Else how will I read the files in an iterative manner?

Answer 2

[Image Analyst]

You need to call load(). Do it once for your reference mat file, then in the loop, do it for all the other files. Something like (untested)

folder = 'C:\Users\Toshiba\Desktop\friday work\';
refFileName = fullfile(folder, '1_1_2.mat');
if ~exist(refFileName, 'file')
  errorMessage = sprintf('Error: reference file does not exist:\n%s', refFileName);
  uiwait(warndlg(errorMessage ));
  return;
end
% Get the reference array.
storedStructure = load(refFileName);
refImage = storedStructure.myImage; % or whatever.
filePattern = [folder, '*.mat'];
matFilenames = dir(filePattern);

% Loop over the other arrays and compare to the ref image.
for k = 1 : numberOfFiles
  thisFileName = fullfile(folder, matFilenames(k).name);
  storedStructure = load(thisFileName);
  thisImage = storedStructure.myImage; % or whatever.
  differenceImage = double(refImage) - double(thisImage);
  rmsDifference(k) = sqrt(sum(differenceImage(:)));
end

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F