Error Brace indexing is not supported

Hi there,

I am having an odd problem, and I'm not sure how to fix the error below. Any assistance would be greatly appreciated.

Brace indexing is not supported for variables of this type.

Many thanks

Following is the code i am using

imageFileNames = imageFileNames(imagesUsed);
originalImage = imread(imageFileNames{1});
Brace indexing is not supported for variables of this type.

class(imageFileNames)

ans =

    'char'

imageFileNames

imageFileNames =

    'rcngvieo ram'



where imagesUsed =

25×1 logical array

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[Stephen23]

"I am having an odd problem"

It is not odd at all: the variable imageFileNames is a character array, for which curly brace indexing is not defined.

Thus the error.

"I'm not sure how to fix the error below. Any assistance would be greatly appreciated."

Do you expect imageFileNames to be a cell array? If so, then you will need to check your code for the place where you replaced the expected cell array with a char array of the exactly same name (because it isn't in the code that you showed us). That will fix the error.

[Life is Wonderful]

@Stephen23,

Do you expect imageFileNames to be a cell array

This is not a cell array, it's a char

class(imageFileNames)

ans =

'char'

[Stephen23]

"This is not a cell array, it's a char "

Sure, which is exactly why you cannot use curly brace indexing with it.

However I did not ask you what it is, I asked you what you expect it to be. A totally different question.

Answer 1

[Image Analyst]

How did you get imageFileNames? Was it from using dir somehow?

% Get file listing of all PNG files in the current folder.
fileList = dir('*.png');
% Convert from structure to cell array.
imageFileNames = {fileList.name};
% Load that cell array into a listbox.
handles.listbox1.String = imageFileNames;

Was it from a listbox of file names that you had loaded up previously? Then you can do

% Get a list of all filenames in the listbox.
imageFileNames = handles.listbox1.String;
% Get the indexes the user selected.
imagesUsed = handles.listbox1.Value;
% Extract the selected names into a subset.
selectedImageFileNames = imageFileNames(imagesUsed);
% Get the name of the first one that was selected:
firstImageFileName = imread(selectedImageFileNames{1});

[EDIT}

Most likely the problem was you did this

imageFileNames = [fileList.name] % Used brackets to concatenate.

instead of this

imageFileNames = {fileList.name} % Should use braces to concatenate.

That will give you spaces in the name and make a long character array, rather than a cell array.

See the FAQ to learn when to use parentheses, braces, and brackets:

https://matlab.fandom.com/wiki/FAQ#What_is_a_cell_array?

[Life is Wonderful]

@Image Analyst

I am using following code , it isn't derived from either dir nor listbox.

% Extract the selected names into a subset.
selectedImageFileNames = imageFileNames(imagesUsed);
% Get the name of the first one that was selected:
firstImageFileName = imread(selectedImageFileNames{1});

[Stephen23]

How do you create imageFileNames ?

[Image Analyst]

What I asked was how you got the original imageFileNames. You did not tell me this.

Like I said

Most likely the problem was you did this

imageFileNames = [fileList.name] % Used brackets to concatenate.

instead of this

imageFileNames = {fileList.name} % Should use braces to concatenate.

[Life is Wonderful]

Yup, I did as you are saying which is derived from the imageDatastore function

imageFileNames = imageDatastore({PathToimageFileNames},"FileExtensions",[".png", ".jpg",".tif"]);

% Detect and localize the tags

[imagePoints, imagesUsed] = detectPatternPoints(detector, imageFileNames.Files);

imageFileNames.Files

[Image Analyst]

That's not how you do it. Try this

imds = imageDatastore({PathToimageFileNames},"FileExtensions",[".png", ".jpg",".tif"]);
imageFileNames = imds.Files

[Life is Wonderful]

It's perfect!!!! You've got the problem under control, now I can see

imageFileNames = imageFileNames(imagesUsed);

K>> class(imageFileNames)

ans =

'cell'

Your proposal work well.

Thank you

Answer 2

[Bora Eryilmaz]

Your imageFileNames variable is not a cell array, so you cannot use brace indexing with it. It is a long char array with words separated by spaces. You can use the split command to generate a cell array of char variables from it:

imageFileNames = 'rcngvieo ram'

imageFileNames = 'rcngvieo ram'

names = split(imageFileNames, ' ')

names = 2×1 cell array
    {'rcngvieo'}
    {'ram'     }

names{1}

ans = 'rcngvieo'

names{2}

ans = 'ram'

[Life is Wonderful]

But then I am facing new error , is this expected ?

Thank you !!

>> names = split(imageFileNames, ' ')

names =

2×1 cell array

{'rcngvieo'}
{'ram'     }

>> imread(names{1} )
Error using imread>get_full_filename
File "rcngvieo" does not exist.

[Bora Eryilmaz]

I am assuming 'ram' is the file extension for your image file. If that is the case, the way you construct the imageFileNames variable is problematic. The imread command needs the full name of the file, including the file extension.

[Life is Wonderful]

No, it was a logical index that was changed to a char rather than a cell.