Numeric N-dimensional array initialization
Hi there ! I'm just starting to use Numeric here, and I'm wondering : how can I efficiently initialize every values of a N-dimensional array, given I don't know the number of dimensions ? I'm looking for something like a map function, or a way to conveniently iterate through the whole N-array, but I didn't find anything ... yet. If anyone has a clue, I'm listening. Thanks -- http://mail.python.org/mailman/listinfo/python-list
Re: Numeric N-dimensional array initialization
I tried to use Numeric.fromfunction, but there seems to be a problem : the function called must have the right number of args (hint : the number of dimensions, which I don't know). So i tried to use a function like : def myfunc(*args, **kw): return 0 and then i get : Numeric.fromfunction(myfunc,(5,5)) 0 I'm a bit puzzled here -- http://mail.python.org/mailman/listinfo/python-list
Re: Numeric N-dimensional array initialization
TG wrote: Hi there ! I'm just starting to use Numeric here, and I'm wondering : how can I efficiently initialize every values of a N-dimensional array, given I don't know the number of dimensions ? I'm looking for something like a map function, or a way to conveniently iterate through the whole N-array, but I didn't find anything ... yet. If anyone has a clue, I'm listening. Since you're just starting, you should know that Numeric is no longer being developed. The actively developed version is numpy: http://www.scipy.org/NumPy You will want to ask numpy questions on the numpy-discussion mailing list. The answers one gets here tend to be hit or miss. https://lists.sourceforge.net/lists/listinfo/numpy-discussion As to your actual question, I'm not entirely sure what you are asking for, but you should look at the .flat attribute. In [5]: from numpy import * In [6]: a = empty((2, 3)) In [7]: a.flat[:] = 10 In [8]: a Out[8]: array([[10, 10, 10], [10, 10, 10]]) # Note, in numpy, .flat is not a real array although it should be usable in most # places that need an array. However, unlike Numeric, it can always be used # even if the array is not contiguous. If you need a real array, use the # .ravel() method, but know that it will make a copy if the array is not # contiguous (for example, if it is the result of a .transpose() call). In [9]: a.flat Out[9]: numpy.flatiter object at 0x196a800 In [10]: a.flat = arange(10) In [11]: a Out[11]: array([[0, 1, 2], [3, 4, 5]]) In [12]: for i in a.flat: : print i : : 0 1 2 3 4 5 -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Numeric N-dimensional array initialization
TG wrote: I tried to use Numeric.fromfunction, but there seems to be a problem : the function called must have the right number of args (hint : the number of dimensions, which I don't know). So i tried to use a function like : def myfunc(*args, **kw): return 0 and then i get : Numeric.fromfunction(myfunc,(5,5)) 0 I'm a bit puzzled here In [24]: def myfunc(*args): : print args : : In [26]: fromfunction(myfunc, (2, 2)) (array([[0, 0], [1, 1]]), array([[0, 1], [0, 1]])) fromfunction() does not iterate over the possible indices and call the function with scalar arguments to get a scalar return value. It generates N arrays with index values in them and calls the function once with those arrays. The return value should be another array. If you actually just want 0s: In [27]: zeros((5, 5)) Out[27]: array([[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]) If you want 1s: In [28]: ones((5, 5)) Out[28]: array([[1, 1, 1, 1, 1], [1, 1, 1, 1, 1], [1, 1, 1, 1, 1], [1, 1, 1, 1, 1], [1, 1, 1, 1, 1]]) If you just want an array as fast as possible because you are going to fill in values later: In [29]: empty((5, 5)) Out[29]: array([[13691, 0, 0, 2883587, 3], [3, 0, 828189706, 6, 0], [0, 9,10, 828202281, 0], [7, 0, 0, 0, 0], [0, 0, 0, 0, 0]]) If you have more complicated needs, we can talk about them on numpy-discussion. -- Robert Kern I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth. -- Umberto Eco -- http://mail.python.org/mailman/listinfo/python-list
Re: Numeric N-dimensional array initialization
Thanks for your precious advices. The flat iterator is definitely what i need. -- http://mail.python.org/mailman/listinfo/python-list
