Take a look at numpy.ix_ http://www.scipy.org/Numpy_Example_List_With_Doc#head-603de8bdb62d0412798c45fe1db0648d913c8a9c
This method creates the index array for you. You only have to specify the coordinates in each dimesion. Bernhard On Oct 29, 8:46 am, "Matthieu Brucher" <[EMAIL PROTECTED]> wrote: > > > Little correction, only c[(2,3)] gives me what I expect, not c[[2,3]], > > which > > > is even stranger. > > > c[(2,3)] is the same as c[2,3] and obviously works as you expected. > > Well, this is not indicated in the documentation. > > c[[2,3]] is refered to as 'advanced indexing' in the numpy book. > > > It will return elements 2 and 3 along the first dimension. To get what you > > want, you need to put it like this: > > > c[[2],[3]] > > > In [118]: c = N.arange(0.,3*4*5).reshape((3,4,5)) > > > In [119]: c[[2],[3]] > > > Out[119]: array([[ 55., 56., 57., 58., 59.]]) > > This is very strange to say the least, as tuple do not work in the same way. > > This does not work however using a ndarray holding the indices. > > > > > > > In [120]: ind = N.array([[2],[3]]) > > > In [121]: c[ind] > > > --------------------------------------------------------------------------- > > <type 'exceptions.IndexError'> Traceback (most recent call > > last) > > > /media/hda6/home/ck/<ipython console> in <module>() > > > <type 'exceptions.IndexError'>: index (3) out of range (0<=index<=2) in > > dimension 0 > > > so you have to convert it to a list before: > > > In [122]: c[ind.tolist()] > > Out[122]: array([[ 55., 56., 57., 58., 59.]]) > > But if I have the coordinates of the points in an array, I have to reshape > it and then convert it into a list. Or convert it into a list and then > convert it to a tuple. I know that advanced indexing is useful, but here it > is not coherent. tuples and lists should have the same result on the array, > or at least it should be documented. > So there is not way to get a sub-array based on coordinates in an array ? > > Matthieu > > -- > French PhD student > Website :http://miles.developpez.com/ > Blogs :http://matt.eifelle.comandhttp://blog.developpez.com/?blog=92 > > _______________________________________________ > Numpy-discussion mailing list > [EMAIL PROTECTED]://projects.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion