How to load MAt file into 3D matrix

I want to load 516 Mat files(240x320)into a 3D Matrix A(240,320,516)

The files are called PVCWARM00071,....,PVCWARM0007516

my code so far:

A = zeros(240,320,516)

nummer=0

>> for i= 1:516

nummer = nummer +1

ext = '.MAT'

naam = 'PVCWARM0007'

file= strcat(naam,num2str(nummer),ext)

A(:,:,i) = load(file)

end

i get the error:Conversion to double from struct is not possible. i already tried to make some adjustments with struct2cell and cell2mat without result.

Can someone help?

Thanks

[Azzi Abdelmalek]

What is the name of your matrix in you mat file?

[Maxim De Roeck]

the 3d matrix is called A, the Mat files are 240x320 arrays without a name

Answer 1

[Evan]

The answer can be found in the documentation of the load function:

S = load(FILENAME) loads the variables from a MAT-file into a structure array, or data from an ASCII file into a double-precision array.

Since you already initialize A as a double, the line A(:,:i) = load(file) is attempting to save load's structure output into your 3D matrix.

If you already know the name of your variables as they are saved in your mat file, you can call load without an output argument to put them in the workspace, then save them to your 3D matrix. Again, though, it helps to know or find out the variable names when doing this:

A = zeros(240,320,516);
nummer = 0;
for i = 1:516
    nummer = nummer +1
    ext = '.MAT';
    naam = 'PVCWARM0007';
    file = strcat(naam,num2str(nummer),ext);
    load(file)
    A(:,:,i) = B; %if, for example, the variable's name is B
end

[Maxim De Roeck]

i understand, but my M-files consists of an 240x320 array filled with values without a name.

[Evan]

What returns when you type the following?

whos -file filename %where filename is the name of your .mat file

[Maxim De Roeck]

so you say that i should make a variable for each file and insert it like that?

[Maxim De Roeck]

>> whos -file PVCWARM00071.MAT Name Size Bytes Class Attributes

PVCWARM00071                  240x320            614400  double              
PVCWARM00071_DateTime           1x7                  56  double              
PVCWARM00071_FrameInfo          1x2                  16  double              
PVCWARM00071_ObjectParam        1x10                 80  double              
PVCWARM00071_Scaling            1x9                  72  double

[Evan]

Okay, so it looks like your variable names are the same as your file names. This means you can just access the arrays using the "file" strings you've already created. Since it looks like each file is going to have a differently named variable, I would return to specifying an output for your load command and just do the following:

A = zeros(240,320,516);
nummer = 0;
for i = 1:516
    nummer = nummer +1
    ext = '.MAT';
    naam = 'PVCWARM0007';
    file = strcat(naam,num2str(nummer),ext);
    S = load(file);
    A(:,:,i) = S.(file);
end

Does that work?

[Maxim De Roeck]

 i fixed it:

for i = 1:516

    eval(['load PVCWARM0007',int2str(i),';']);
    eval (['A(:,:,i) = PVCWARM0007',int2str(i),';']);
end

thanks anyway!!

[Evan]

The method you're using is not recommended, which is why I suggested using dynamic field references. See Azzi's link for an explanation of why eval should be avoided. You also might find this page helpful.

Answer 2

[Azzi Abdelmalek]

A = zeros(240,320,516)  
nummer=0
for i= 1:516
  nummer = nummer +1
  ext = '.MAT'
  naam = 'PVCWARM0007'
  file= strcat(naam,num2str(nummer),ext)
  variable_name=whos('-file',file);
  x=load(file)
  A(:,:,i) = x.(variable_name.name)
end

[Maxim De Roeck]

i fixed it:

for i = 1:516
  eval(['load PVCWARM0007',int2str(i),';']);
  eval (['A(:,:,i) = PVCWARM0007',int2str(i),';']);
end

thanks anyway!!

[Azzi Abdelmalek]

Why eval() and evalin() are not recommended?