Output argument <XX> (and possibly others) not assigned a value in the execution with <YY> function

Question

Bao Ngo 2022-2-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1656380-output-argument-xx-and-possibly-others-not-assigned-a-value-in-the-execution-with-yy-function

评论： Bao Ngo 2022-2-23

I have a function script as follows:

function [h]=getColorHist(im, color_table, opt) 
    im = rgb2hsv(im);   
    [ht,wid,~]=size(im);
    if opt == 'euc' % euclidean distance
    D = pdist2(color_table, reshape(im, [ht*wid, 3]));
    end
end

I call this function from a different script HW3.m from the command line and get the following error:

HW3

Output argument "h" (and possibly others) not assigned a value in the execution with "getColorHist"

function.

Error in HW3 (line 23)

f_hist(f_cnt, :) = getColorHist(hsv_im, color_table,'euc')

where HW3.m is:

im_path='/MATLAB Drive/Published/NWPU-RESISC45_1';
ids = {'airplane', 'airport', 'baseball_diamond', 'baseball_court', 'beach','bridge','chaparral', 'church', 'circular_farmland', 'cloud','commercial_area','dense_residental', 'desert', 'forest', 'freeway'};
kColor = 64;
color_table = getHSVColorTable_2(im_path, ids, kColor);
nClass = length(ids); nImg = 40; 
f_hist = zeros(nImg*nClass, kColor);
labels = zeros(nImg*nClass, 1);
f_cnt = 0;
for k=1:nClass
    % list of files
    class_path = sprintf('%s/%s', im_path, ids{k});
    f_list = dir(sprintf('%s/*.jpg', class_path));
    offs = randperm(length(f_list));
    % load random 256 pixels from each images
    if isempty(offs) == 0
        for j=1:nImg
            f_cnt = f_cnt + 1;
            % read in a random image from the class
            im = imread(sprintf('%s/%s', class_path, f_list(offs(j)).name)); 
            hsv_im = rgb2hsv(im);
            f_hist(f_cnt, :) = getColorHist(hsv_im, color_table,'euc');
            labels(f_cnt) = k;
            % plot
            if (1)
                figure(3); subplot(nClass, nImg, f_cnt); 
                plot(f_hist(f_cnt, :)); grid on;
            end
        end
    end 
end

Can anyone check whether my code has any errors to let this problem occur? This is mind-boggling to me, appreciate any help!

Here this the script for function getHSVColorTable_2 in HW3.m:

function [color_table]=getHSVColorTable_2(im_path, ids, kColor)
dbg=1;
if dbg
   im_path='/MATLAB Drive/Published/NWPU-RESISC45_1';
   ids = {'airplane', 'airport', 'baseball_diamond', 'baseball_court', 'beach','bridge','chaparral', 'church', 'circular_farmland', 'cloud','commercial_area','dense_residental', 'desert', 'forest', 'freeway'};
   kColor = 64;
end
nClass = length(ids); nImg = 40; nPixelPerImage = 256;
% sample images from the repository to train a global HSV color table
% training pixels
x = zeros(nImg*nPixelPerImage*nClass, 3); cnt = 0; 
for k=1:nClass
    % list of files
    class_path = sprintf('%s/%s', im_path, ids{k});
    f_list = dir(sprintf('%s/*.jpg', class_path));
    offs = randperm(length(f_list));
    % load random 256 pixels from each images
    if isempty(offs) == 0
        for j=1:nImg
            % read in a random image from the class
            im = imread(sprintf('%s/%s', class_path, f_list(offs(j)).name)); 
            hsv_im = rgb2hsv(im); 
            [ht,wid,~] = size(im);
            hsv_im = reshape(hsv_im, [ht*wid, 3]);
            pix_offs = randperm(ht*wid); 
            x(cnt+1:cnt+nPixelPerImage, :) = hsv_im(pix_offs(1:nPixelPerImage), :);
            cnt = cnt + nPixelPerImage;
        end
        % plot
        if dbg
            figure(1); subplot(1, nClass, k); 
            subplot(1, nClass, k); imshow(im); title(ids{k});
        end
    end 
end

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Answer 1

KSSV 2022-2-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1656380-output-argument-xx-and-possibly-others-not-assigned-a-value-in-the-execution-with-yy-function#answer_902525

在 MATLAB Online 中打开

The error is simple. In the given function:

function [h]=getColorHist(im, color_table, opt) 
    im = rgb2hsv(im);   
    [ht,wid,~]=size(im);
    if opt == 'euc' % euclidean distance
    D = pdist2(color_table, reshape(im, [ht*wid, 3]));
    end
end

The output seeked is h. Did you see any variable calculated in the function on the name h? No, the variable is not ther ein the function and you are trying to take it as output, so the error pops out.

I think the output should not be h, it shoudle be D. Change the function to:

function D=getColorHist(im, color_table, opt) 
    im = rgb2hsv(im);   
    [ht,wid,~]=size(im);
    if opt == 'euc' % euclidean distance
    D = pdist2(color_table, reshape(im, [ht*wid, 3]));
    end
end