I have a set of data-points for the value of `z` depending on `x` and `y`. I am searching for some method in order to interpolate `zi` for the for `xi`, `yi`.

The problem is that `x` and `y` are not distributed in an orthogonal grid. Instead the grid-points `x` and `y` are distributed randomly.

Is there any MATLAB function for this available? (Ideally in standard MATLAB w/o specialized packages - e.g. statistic toolbox or others).