Unable to use a value of type cell as an index

Question

Muhammad Hilmi Al Farid Ni'man 2021-11-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1576198-unable-to-use-a-value-of-type-cell-as-an-index

回答： yanqi liu 2021-11-1

在 MATLAB Online 中打开

so I'm trying to detect a circle on a plate but i always got an error at line 18

Unable to use a value of type cell as an index.

Error in xxxx (line 18)

for k = 1:length(B)

addpath 'xxxxxx'
RGB = imread('xxx.jpg');
I = imadjust(RGB, [0.2; 0.3], [0.2; 0.3])
imtool(I)
imshow(I)
I = rgb2gray(I);
bw = imbinarize(I);
imshow(bw)
bw = bwareaopen(bw,30);
se = strel('disk',2);
bw = imclose(bw,se);
imshow(bw)
[B,L,N] = bwboundaries(bw);
figure; imshow(bw); hold on;
for k = 1:length(B)
    boundary = B{k};
    if(k > N)
        plot(boundary(:,2), boundary(:,1), 'r', 'LineWidth', 2);
    elseif(k < N)
        plot(boundary(:,2), boundary(:,1), 'b', 'LineWidth', 2);
    else
        plot(boundary(:,2), boundary(:,1), 'g', 'LineWidth', 2);
    end
end
stats = regionprops (L, 'Perimeter')
for k = 1:length(B)
    if (k <= N)
        boundary = B{k}
        perimeter = stats(k).Perimeter
        if perimeter < 1000
            length = perimeter/4.05
            lenght_real = 30
            c = lenght_real/length
            metric_string = sprintf('%2.2f', length_real)
            text(boundary(1,2)+20,boundary(1,1)+50,meteric_string,'Color','g','FontSize',12,'FontWeight','bold')
        end
    else
        boundary = B{k}
        perimeter_c = stats(k).Perimeter
        length = perimeter/4.05
        lenght_real = 30
        c = lenght_real/length
        if perimeter_c > 120
            diameter = perimeter_c/pi
            diameter_real = c*diameter
            metric_string = sprintf('%2.2f', diameter_real)
            text(boundary(1,2)-10,boundary(1,1)-40,meteric_string,'Color','r','FontSize',12,'FontWeight','bold')
        else
            diamter = perimeter_c/pi
            diamter_real = c*diamter
            metric_string = sprintf('%2.2f', diameter_real)
            text(boundary(1,2)-10,boundary(1,1)-40,meteric_string,'Color','r','FontSize',12,'FontWeight','bold')
        end
    end
    title(['Diameter of middle hole and ',...
        'Length if block gauge in millimeters'])
end

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James Tursa 2021-11-1

Please post the entire error message, including the offending line.

Muhammad Hilmi Al Farid Ni'man 2021-11-1

so the entire error mesaage is just

Unable to use a value of type cell as an index.

Error in xxxx (line 18)

for k = 1:length(B)

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Answer 1

Steven Lord 2021-11-1

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1576198-unable-to-use-a-value-of-type-cell-as-an-index#answer_821178

在 MATLAB Online 中打开

Don't use length as a variable name. If your code does, you will not be able to call the length function.

length = perimeter/4.05

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Answer 2

yanqi liu 2021-11-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1576198-unable-to-use-a-value-of-type-cell-as-an-index#answer_821198

在 MATLAB Online 中打开

addpath 'xxxxxx'
RGB = imread('xxx.jpg');
I = imadjust(RGB, [0.2; 0.3], [0.2; 0.3]);
imtool(I)
imshow(I)
I = rgb2gray(I);
bw = imbinarize(I);
imshow(bw)
bw = bwareaopen(bw,30);
se = strel('disk',2);
bw = imclose(bw,se);
imshow(bw)
[B,L,N] = bwboundaries(bw);
figure; imshow(bw); hold on;
for k = 1:numel(B)
    boundary = B{k};
    if(k > N)
        plot(boundary(:,2), boundary(:,1), 'r', 'LineWidth', 2);
    elseif(k < N)
        plot(boundary(:,2), boundary(:,1), 'b', 'LineWidth', 2);
    else
        plot(boundary(:,2), boundary(:,1), 'g', 'LineWidth', 2);
    end
end
stats = regionprops (L, 'Perimeter');
for k = 1:numel(B)
    if (k <= N)
        boundary = B{k};
        perimeter = stats(k).Perimeter;
        if perimeter < 1000
            len = perimeter/4.05;
            len_real = 30;
            c = len_real/len;
            metric_string = sprintf('%2.2f', len_real_real);
            text(boundary(1,2)+20,boundary(1,1)+50,meteric_string,'Color','g','FontSize',12,'FontWeight','bold');
        end
    else
        boundary = B{k};
        perimeter_c = stats(k).Perimeter;
        len = perimeter/4.05;
        len_real = 30;
        c = len_real/len;
        if perimeter_c > 120
            diameter = perimeter_c/pi;
            diameter_real = c*diameter;
            metric_string = sprintf('%2.2f', diameter_real);
            text(boundary(1,2)-10,boundary(1,1)-40,meteric_string,'Color','r','FontSize',12,'FontWeight','bold');
        else
            diamter = perimeter_c/pi;
            diamter_real = c*diamter;
            metric_string = sprintf('%2.2f', diameter_real);
            text(boundary(1,2)-10,boundary(1,1)-40,meteric_string,'Color','r','FontSize',12,'FontWeight','bold');
        end
    end
    title(['Diameter of middle hole and ',...
        'len_real if block gauge in millimeters'])
end