I want to print numpy arrays nicer, using the indices into the array [0 1] indexes row zero and column one:
Suppose we have a big numpy array
x = np.arange(400*8000).reshape(400,8000).astype(float)
Now we want to print row 100, but only the last ten entries:
print x[100, -10:]
This should result in something like:
Index | X
[ 100 7990] | 807990
[ 100 7991] | 807991
[ 100 7992] | 807992
[ 100 7993] | 807993
[ 100 7994] | 807994
[ 100 7995] | 807995
[ 100 7996] | 807996
[ 100 7997] | 807997
[ 100 7998] | 807998
[ 100 7999] | 807999
I produced this by getting the index as follows:
index = np.indices(X.shape)[:, 100, -10:]
print index
# array([[ 100, 100, 100, 100, 100, 100, 100, 100, 100, 100],
# [7990, 7991, 7992, 7993, 7994, 7995, 7996, 7997, 7998, 7999]])
But this seems to be very inefficient, especially, when the indexing gets more complicated, or X gets bigger (As in billions of entries).
Is there a better way of creating index arrays from an index (here the index is [100, -10:] and the index array is index)?
