Undefined function or variable 'sigshift'. how can i shift the signal?

i got this code

nx = [-3:3]; x = [-4 5 1 -2 -3 0 2];

subplot(2,2,1);

stem(nx,x); 

axis([-4 8 -5 9]);

ny = [-1:5];

   y = [6 -3 -1 0 8 7 -2];

subplot(2,2,2);

stem(ny,y); 

axis([-4 8 -5 9]);

[c,nc]=sigshift(y,ny,2);

subplot(2,2,3);

stem(nc,c); 

axis([-4 8 -5 9]);

[u,nu] = sigadd(x,nx,c,nc);

subplot(2,2,4);

stem(nu,u); 

axis([-4 8 -5 9])

and i got =>

Undefined function or variable 'sigshift'.

Error in hw2a (line 9)
[c,nc]=sigshift(y,ny,2);

Answer 1

[Walter Roberson]

sigshift() is a minor function that can be found in http://www.mathworks.com/matlabcentral/fileexchange/2189-digital-signal-processing-using-matlab

[Masudur Rahman]

then what to do

please help