vorticity in pipe flow
 

Dear All,
I am using PIV data for a pipe flow in matlab to calculate vorticity. After reading PIV data in matlab, it appears to be of these values. x=<39*31 double>, y=<39*31d ouble>,u=<39*31*204 double>,v=<39*31*204 double>. Now when I try to use curl command it gives me a message "U,V must all be a 2D arrays."
I have also calculated partial derivatives of u and v like this [dudx,dudy] = gradient(u,h);[dvdx,dvdy] = gradient(v,h). Do I just have to subtract dvdy-dudx to get vorticity? Again it will appear of value this vorticity=<39*31*204 double>. Please guide.
Thanks