Sobel function error in image

I edit the code but again there is an error

I=imread('first palm.jpg'); 
subplot(1,2,1); 
imshow(I);title('first palm'); 
BW1=edge(I,'sobel'); 
BW2=edge(I,'canny'); 
subplot(1,2,2); 
imshow(BW1);
title('sobel edge detector image'); 
subplot(1,2,1);
imshow(I);
title('first palm'); 
subplot(1,2,2); 
imshow(BW2);title('canny edge detector image');

and this error "Error in Edges (line 4) BW1=edge(I,'sobel');" appear to me

[eltaf kazemi]

most of these are for gray scale images.

I suggest using "rgb2gray"

Answer 1

[Image Analyst]

If you still care, is I an RGB image or gray scale?