[SciPy-user] Create n-dim array from axis

[Vincent Schut]

> 
> This is a good example for using slices and mgrid and is much better
> for regularly spaced grids (representable of slices) than what I had.
> However, what I also needed in the past was building a grid for
> arbitrary points in each dimension
> 
> a made-up example
> x = [2, 3, 5, 10]
> y = [0, 1]
> z = [100, 200, 500, 1000]
> create_array(x, y, z)
> ?
> 
Hmm, tricky...
I'd go for something like this:

def create_array2(nodes):
     # nodes is a list with lists of axis points (e.g. [[2, 3, 5, 10], 
[0, 1], [100, 200, 500, 1000]]
     shape = tuple([len(a) for a in nodes])
     idx = numpy.indices(shape)
     result = numpy.zeros(idx.shape, numpy.float)
     for d in range(idx.shape[0]):
         result[d] = numpy.take(nodes[d], idx[d])
     return result.transpose()

create_array2([[0.0, 0.5, 1], [2.0, 2.5, 3]])


though this stil contains a loop which might be avoidable... It ought to 
be pretty generic though. It's the end of the working day here, and I'm 
starting to get a bit fuzzy in the brains, so better solutions might 
very well be possible.

Vincent.