matlab 问题

I keep getting this error "Undefined function 'vl_sift' for input arguments of type 'single'.".....can anyone explain what this is/

Kotti - where in your code are using calling vl_sift?
The error message is telling you (at least) one of two things - either vl_sift does
not accept inputs of type single or
MATLAB cannot find the function. In the Command Window, type

which vl_sift -all

What do you see as the result? If 'vl_sift' not found. appears, then you do not have the function or it is not in the MATLAB search path. If the latter, then just add the folder that contains this file
to the path.