Dot indexing error for naming variable

Hi, I have a loop for processing images using the following code;

path='C:\Users\Udi\Desktop\3rd Year Project\2. GMM\new folder';

I = dir(fullfile(path, '*.jpg'));

for k = 1:numel(I)
    filename = fullfile(path, I(k).name);
    I2 = imread(filename);
    b = I2(:,:,1);
    d.(k)= uint8(b) .* uint8(b>180);
    %figure, imshow(d)
    e.(filename)=d{k}(d{k}>0);
    save([filename, 'threshold', '.mat'], 'd.(k)')
end

I am saving every output of d and would like the variable to be named as d_k (where k is the number of iteratoin)

I keep getting this error though,

Unable to perform assignment because dot indexing is not supported for variables of this type.

Any help would be appreciated!

Answer 1

[Walter Roberson]

Either variable d or e exists already and is not a structure.

d.(k)= uint8(b) .* uint8(b>180);

The above line is a problem: k is a number, and using a number as a dynamic field name is not supported. You might want d{k} as suggested by your later use of d{k}

e.(filename)=d{k}(d{k}>0);

You constructed filename from an entire path including directory. It is likely to be too long for a field name, and it will include path separators which are not valid for field names. You would probably be better off storing the filename in a data structure and using a numeric index for what you are storing separately.

    save([filename, 'threshold', '.mat'], 'd.(k)')

filename ends in .jpg so you would be constructing a new filename that might look like

   C:\Users\Udi\Desktop\3rd Year Project\2. GMM\new folder\rhinos.jpgthreshold.mat

which is unlikely to be what you want.

It is also not possible to save() part of a variable, only an entire variable. You can save all of d but to save the current d{k} you would have to assign that to a variable and save the variable.

  e.(filename)=d{k}(d{k}>0);

The right hand side of that is probably valid, but be warned that it produces a vector result in which you cannot tell where the values came from. Is that what is desired?

     b = I2(:,:,1);

It is a bit confusing to name the red channel b

[Stephen23]

"You would probably be better off storing the filename in a data structure..."

It already is: I.

"... and using a numeric index for what you are storing separately"

Easy using I:

I(k).data = ...

[udi ibgui]

Thanks! When I use curly brackets though {}, I still get an error

Unable to perform assignment because brace indexing is not supported for variables of this type.

Error in loop_code (line 9)

d{k}= uint8(b) .* uint8(b>180);