interp2
Two dimensional interpolation.
` (zn,interploator)=interp2(x,y,z,xn,yn,option)`
` (zn,interploator)=interp2(x,y,z,xn,yn)`
` yn=interp2(interpolator,xn);`
 Inputs `x` A real vector sepcifying the x-coordinates of points at which the function values are known. `y` A real vector sepcifying the y-coordinates of points at which the function values are known. `z` A real array, containing the values of the function to be interpolated at the points defined by the first two inputs. `xn` A real array, containing the x-coordinates of the points at which the interpolated values of the function are needed. `yn` A real array, containing the y-coordinates of the points at which the interpolated values of the function are needed. `interpolator` the second output of a prior call to `interp2` . `option` `'nn'` for nearest neigbor interpolation, `'linear'` for linear interpolation, `'cubic'` for piecewise cubic interpolation, and `'spline'` for spline interpolation. The default value of `option` is `'cubic'` . Outputs `zn` The interpolated values of the function at the points specified by `xn` . `interpolator` An object that can be used subsequently to interpolate the same function at other points by using the last form of call to `interp2` .

Example
```>>x=[0:.25:1]'*pi;
>>z=sin(x)*cos(x')
>>xn=[0:.05:1]'*pi;
>>(xn,yn)=meshgrid(xn,xn);
>>zn=interp2(x,x,z,xn,yn);
>>subplot(2,1,1)
>>surf(x,x,z)
>>title('Coarse Grid')
>>subplot(2,1,2)
>>surf(xn,yn,zn)
>>title('Fine Grid (Interpolated)')
``` 