MATLAB: Can you help me? i want to show min and max value on RGB image with histogram, but is not work correctly

Question

%this is my code, and error report

[filename,pathname] = uigetfile({'*.jpg;*.bmp'},'Select an Image');
I = imread([pathname filename]);
imshow(I);
[bw, rgb]=hsvth(I);
figure, imshow(bw);
figure, imshow(rgb);
img1 = imcrop(rgb);
img2 = imcrop(rgb);
%imshow(img1);
%imshow(img2);
%I=imread('autumn.tif');
%Histogram
R=img1(:,:,1);
G=img1(:,:,2);
B=img1(:,:,3);
figure, 
subplot(3,1,1)
imhist(R)
subplot(3,1,2)
imhist(G)
subplot(3,1,3)
imhist(B)
%R Value
red_min=min(min(R(:,:,1)))
red_max=max(max(R(:,:,1)))
%G Value
green_min=min(min(G(:,:,2)))
green_max=max(max(G(:,:,2)))
%B Value
blue_min=min(min(B(:,:,3)))
blue_max=max(max(B(:,:,3)))

Answer 1

%R Value
red_min=min(R(:)) ; 
red_max=max(R(:)) ; 
%G Value
green_min=min(G(:)) ; 
green_max=max(G(:)) ;
%B Value
blue_min=min(B(:)) ; 
blue_max=max(B(:)) ;

Note that G, B are 1D matrices. So don't use 2 and 3. You need not to use min twice.