diff options
Diffstat (limited to 'numpy/doc/indexing.py')
| -rw-r--r-- | numpy/doc/indexing.py | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/numpy/doc/indexing.py b/numpy/doc/indexing.py index 15383388c..d68c86017 100644 --- a/numpy/doc/indexing.py +++ b/numpy/doc/indexing.py @@ -234,12 +234,12 @@ array corresponding to all the true elements in the boolean array. As with index arrays, what is returned is a copy of the data, not a view as one gets with slices. -With a multidimensional index array, multidimensional arrays may be -the result. For example: :: +Multidimensional arrays may result, if y has more dimensions than b. +For example: :: - >>> b[:,5] # use a 1-D boolean that broadcasts with y + >>> b1 = b[:,5] # use a 1-D boolean whose first dim agrees with the first dim of y array([False, False, False, True, True], dtype=bool) - >>> y[b[:,5]] + >>> y[b1] array([[21, 22, 23, 24, 25, 26, 27], [28, 29, 30, 31, 32, 33, 34]]) @@ -247,9 +247,14 @@ Here the 4th and 5th rows are selected from the indexed array and combined to make a 2-D array. In general, when the boolean array has fewer dimensions than the array -being indexed, the shape of the result is the number of True elements -of the boolean array followed by the remaining dimensions of the array -being indexed. For example, using a 2-D boolean array of shape (2,3) +being indexed, this is equivalent to y[b, ...], which means +y is indexed by b followed by as many : as are needed to fill +out the rank of y. +Thus the shape of the result is one dimension containing the number +of True elements of the boolean array, followed by the remaining +dimensions of the array being indexed. + +For example, using a 2-D boolean array of shape (2,3) with four True elements to select rows from a 3-D array of shape (2,3,5) results in a 2-D result of shape (4,5): :: @@ -268,6 +273,8 @@ with four True elements to select rows from a 3-D array of shape [20, 21, 22, 23, 24], [25, 26, 27, 28, 29]]) +For further details, consult the numpy reference documentation on array indexing. + Combining index arrays with slices ================================== |