I would like to remove a specific character from a 2d numpy array. For example:
myarr = np.array([[2,"?",5,2,3,6,8],[6,7,8,9,"?"]])
How can I delete "?" without loosing the structure of the array? My result should look like this:
[[2,5,2,3,6,8]
[6,7,8,9]]
(I am using Python 3.4.2 and numpy 1.9 on a Win7 machine)
myarr = np.array([[2,"?",5,2,3,6,8],[6,7,8,9,"?"]]) produces
array([[2, '?', 5, 2, 3, 6, 8], [6, 7, 8, 9, '?']], dtype=object)
That is an array of 2 items of type object. There isn't an 'structure'. This is basically the same as a list of lists
mylist = [[2, '?', 5, 2, 3, 6, 8], [6, 7, 8, 9, '?']]
A simple way of removing the '?' is:
for l in mylist:
l.remove('?')
But this raises a ValueError if there isn't any '?' in the sublist, and does not remove all if there is more than one. Both of those faults could be fixed by writing a small function that counts the number of occurrences, and removes the right number. Can you handle that function?
So the problem comes down to removing selected elements from a list of lists (or array of lists).
the 'remove all' function is simpler than I thought:
def remove_all(a,x):
while x in a:
a.remove(x)
for a in myarr:
a.remove_all('?')
Numpy arrays must be "rectangular", that is, all rows/columns must have the same length. Your example looks like you need a "jagged array", which numpy doesn't support.
If this is just a case of poorly-picked example, you can remove the ? elements by selecting all non-? elements:
result = myarr[myarr!='?']
