using parfor loop

I am trying to run a paralell loop where for every nth iteration of i, j will jump up by a pre-determined amount.

this is my attempt function [x]= displacementsi(i,z,nx,ny) n = 1:nx; m = upsample(n,ny); h = ones(nx,1);

parfor j = filter(h,1,m)

x(1:4)=z((2*i)-(j-2):(2*i)+(j+1))

end end

I get this error

??? Undefined function or variable 'parforstart'.

Error in ==> displacementsi at 4 h = ones(nx,1);

Error in ==> fe_test at 112 [x] = displacementsi(i,displacements,nx,ny);

how can I operate the task as above without the error.

Thanks