How to use arguments validation functions for multi-frame images?

Hi, I am designing a function to analyse an image sequence frame by frame to return a vector of time according to the cardiac cycle. For the image file argument validation, how do I customise a validation function for these two purposes:

1) ensure each sequence have a reasonable duration (number of frames, minimum 75 frames in total) 2) must be a 3D array

Thanks in advance!

function peaktimes = detectCardiacPhase(img, frameRate)
arguments 
    img (:,:,:) {mustBeNumeric} 
    frameRate double {mustBePositive} = 15 %default value of frameRate is 15 frames/sec
    end
end

Answer 1

[Ashutosh]

From what I am understanding, you need your function to perform 2 preliminary checks on any input video (or in other words, image sequence) file:

1. Video file must have at least 75 frames, ie the sequence must have at least 75 images.
2. The image sequence must be 3 dimensional. I am assuming you mean each image is 2 dimensional and each image in the sequence is stacked on top of each other to make the sequence 3 dimensional. Hence the third dimension (or depth) of the sequence is equal to the number of frames in sequences

I will admit I am not entirely sure I got these right, so let me know if something is amiss.

You can check the 2 conditions as follows:

function peaktimes = detectCardiacPhase(img, frameRate) 
    errorMsg1 = "The entered sequence is not 3D";
    errorMsg2 = "The entered sequence is too short";
    if length(size(img)) ~= 3 % check if input is 3D
        error(errorMsg1);
    elseif size(img,3) < 75 % check if there are at least 75 frames
        error(errorMsg2);
    end
    % main 
    % function
end

You can also refer to the documentation for the error function.

[Wei Yow]

Thank you very much. It worked!