How to implement sgolay filter in matlab GUI?

i want to implement Sgolay filter in MATLAB GUI PLZ giude me: i created a GUI with a push button and axes. in the push button call back function i typed the following code:

function output_Callback(hObject, eventdata, handles)

load('ecgdat.mat')

sig=val(1,:).'

filt_op= sgolayfilt(sig,0,21);

axes(handles.axes2)

plot(1:length(filt_op), filt_op)

I am getting error.. PLZ tell me how to fix this

[Geoff Hayes]

pavan - please copy and paste the full error message to this question.