I would like to select the x, y values from an array of the same, for example :
xy = [[0.0, 3], [0.1, 1], [0.2, -1]]
where y > 0, so the output should be
array[ [0.0, 3], [0.1, 1]]
I tried something like
[x for x in xy if y>0]
, but it returns the following error :
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all().
slice the object to compare just the y values and use the resulting boolean mask:
In [12]:
xy[xy[:,1]>0]
Out[12]:
array([[ 0. , 3. ],
[ 0.1, 1. ]])
Here xy[:,1] gives you just the y values:
In [13]:
xy[:,1]
Out[13]:
array([ 3., 1., -1.])
Here is the resultant boolean mask:
In [14]:
xy[:,1] > 0
Out[14]:
array([ True, True, False], dtype=bool)
Try this :
ans = [i for i in xy if i[1] > 0]
Output :
[[0.0, 3], [0.1, 1]]
[[x, y] for x, y in xy if y > 0]
numpy.array(ans).flatten() , if you want a single list.Another approach using itertools.compress:
from itertools import compress
xy = [[0.0, 3], [0.1, 1], [0.2, -1]]
res = compress(xy, [item[1] > 0 for item in xy])
Output:
>>> list(res)
[[0.0, 3], [0.1, 1]]
try this:
[x for x in xy if x[1]>0]
>= 0?