Thread: incompatible pointer type?

Hey,
I need to pass a **pointer of an array as a function argument, but for some reason I keep getting the error "warning: assignment from an incompatible pointer type". As you can tell I'm pretty new to using C, so I'll post my code and hope someone can point out the blatant error .

double x[2][2],y[2][2];
double **u;
double **v;

x[0][0]=x[1][0] = 4;
x[0][1]=x[1][1] = -3;

y[0][0]=y[1][0] = 1;
y[0][1]=y[1][1] = -1;

u = &x; //this is where the compiler error occurs.
v = &y;

functioncall(u,v); //these arguments need to be of the type const double**

Cheers for any help,
Kieran