Hi everybody,

I have a sample of points for a multivariate function that I would like to approximate with interpolation, where all arguments are on a grid. I would like to get a value for that function for other (interior) arguments but I get something wrong in the syntax.

I am open to using Dierckx or other packages. Quadratic interpolation would be nice but I would already be happy with linear.

Here is a minimal example:

```
using Interpolations
grid = 0:7
fun(a,b) = sin(b) + 0.1a^2
y = [fun.(a,b) for a in grid, b in grid]
```

Following the syntax for univariate functions: `LinearInterpolation(grid, sin.(grid))`

, I tried `LinearInterpolation(grid, grid, y)`

and `LinearInterpolation(y)`

but I get a MethodError.

Then I tried :

```
itp = interpolate(y, BSpline(Linear()))
extrapolate(itp, [0.3, 0.8]) #returns a extrapolate(interpolate(Matrix))
#expected result: approximation of the true function at (0.3, 0.8)
julia> fun(0.3, 0.8)
0.7263560908995228
```

Thank you in advance for any tip !