MATLAB: How to give a correct file name

cell arraysdigital image processing

I have a 3D face image dataset. I need to load it as a multidimensional array, rows represent diff people and columns represent diff expressions. For my code below, j represent no of people and k represent no of expressions (for an example, i just use 2 people with 4 different expressions each).The images are named from 101 until 104 for the first person, and 201 until 204 for the second one.Then, i need to concatenate the arrays.When i run the code, an error occured saying 'invalid file identifier'. I think the file name(formatSpec) i gave is incorrect. Anyone have an idea?Also, the variable A suppose to be in 3 dimension, but there's no result for it.Thank you.

j=2;
k=4;
mydata = cell(j,k);
%
for p = 1:j
    for  e = 1:k
        people = sprintf('%d%0d.txt' , p);
        expression = sprintf('%d%02d.txt' , e);
        fname = strcat(people,expression)
        fid = fopen(fname);
        A = fscanf(fid, '%f %f %f');
        mydata{p,e} = A
        fclose(fid);
    end
end

Best Answer

Replace

people = sprintf('%d%0d.txt' , p);
expression = sprintf('%d%02d.txt' , e);
fname = strcat(people,expression)

fname = sprintf('%d%02d.txt', p, e )

which outputs

fname =
204.txt

Related Solutions

MATLAB: Changing the dimension representation

First, a piece of advice, use variable names that have meaning, preferably full words. It's impossible to tell from their name alone what j, k, e, p represent. personcount, expressioncount, person, expression, are much clearer. Even mydata is not very good, it doesn't say what kind of data it holds. I assume images of people expression, so imgexpression would be better.

Second, there is nothing in the snippet you've posted that depends on the order of the dimension. If you swap the order of the dimensions, the only two lines that need to change are the array declaration and the assignment to it (which you haven't shown). Certainly not the order of the loops, nor the sprintf call. So:

expressioncount = 4;
personcount = 2;
imgexpression = cell(personcount, expressioncount);
%or if you swap:
%imgexpression = cell(expressioncount, peoplecount);
%the loop order does not matter one bit
for person = 1:personcount
   for expression = 1:expressioncount
      fname = sprintf('%d%02d.txt', person, expression); %according to your description this is what you should be using
      fid = fopen(fname);
      %... some code
      %at some point you need to do the assignment
      imgexpression{person, expression} = ...
      %if you swap:
      %imgexpression{expression, person} = ...
   end
end

MATLAB: How to make ‘for’ loops to represent rows and columns

You get "error using fscanf.Invalid file identifier" because the fid in the fscanf call is invalid. The fid is invalid because fopen failed. When dealing with i/o operations, it's always a good idea to check that it succeeds. e.g.:

fid = fopen(fname);
if fid == -1
  %file failed to open
  error('Failed to open %s', fname);
end

Most likely, the fopen failed because your filename is invalid. That would be because your format string in the sprintf call is incorrect. Possibly, you meant:

fname = sprintf('%d%02d.txt', p, e);

This will create '105' out of p = 1, e = 5; '114' out of p = 1, e = 14; '1005' out of p = 10, e = 5; and '1014' out of p = 10, e = 14.

Best Answer

Related Solutions

MATLAB: Changing the dimension representation

MATLAB: How to make ‘for’ loops to represent rows and columns

Related Question