I=imread('f:oli.tif');
I2=nlfilter(I,[3 3],'std2');
imshow(I2)

Error using iptcheckinput
Function NLFILTER expected its first input, A, to be two-dimensional.

Error in nlfilter>parse_inputs (line 134)
iptcheckinput(a,{'logical','numeric'},{'2d'},mfilename,'A',1);

Error in nlfilter (line 51)
[a, nhood, fun, params, padval] = parse_inputs(varargin{:});

Error in Untitled21111111 (line 2)
I2=nlfilter(I,[3 3],'std2');

I=imread('f:oli.tif');
I2=nlfilter(rgb2gray(I),[3 3],'std2');
imshow(I2)