运行edge进行sobel边缘检测出现的问题

>> BW=edge(J,'sobel');
??? Error using ==> images\private\checkinput>check_attributes
Function EDGE expected its first input argument, I,
to be two-dimensional.

Error in ==> images\private\checkinput at 37
check_attributes(A, attributes, function_name, variable_name, ...

Error in ==> edge>parse_inputs at 502
checkinput(I,{'double','logical','uint8','uint16'},...

Error in ==> edge at 161
[a,method,thresh,sigma,H,kx,ky] = parse_inputs(varargin{:})
运行edge进行sobel边缘检测,结果不行
出现了几个错误,请高手看看这是什么问题
我很菜,先谢谢了.