How can I duplicate a row or column in a numpy array?
2 answers
Approach # 1
One approach with np.insert
-
np.insert(a,2,a[1],axis=0)
For duplicate columns use it along axis=1
-
np.insert(a,2,a[:,1],axis=1)
Place as functions to have total number of duplicates -
def dup_rows(a, indx, num_dups=1):
return np.insert(a,[indx+1]*num_dups,a[indx],axis=0)
def dup_cols(a, indx, num_dups=1):
return np.insert(a,[indx+1]*num_dups,a[:,[indx]],axis=1)
Example run -
In [82]: a
Out[82]:
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
In [83]: np.insert(a,2,a[1],axis=0)
Out[83]:
array([[0, 1, 2],
[3, 4, 5],
[3, 4, 5],
[6, 7, 8]])
In [141]: np.insert(a,2,a[:,1],axis=1)
Out[141]:
array([[0, 1, 1, 2],
[3, 4, 4, 5],
[6, 7, 7, 8]])
Total mileage -
In [255]: a
Out[255]:
array([[19, 65, 87, 46, 85],
[18, 45, 90, 26, 31],
[49, 35, 34, 62, 24],
[47, 85, 63, 91, 33],
[54, 37, 89, 79, 50],
[53, 54, 66, 59, 38]])
In [256]: dup_rows(a, indx=4, num_dups=3)
Out[256]:
array([[19, 65, 87, 46, 85],
[18, 45, 90, 26, 31],
[49, 35, 34, 62, 24],
[47, 85, 63, 91, 33],
[54, 37, 89, 79, 50],
[54, 37, 89, 79, 50],
[54, 37, 89, 79, 50],
[54, 37, 89, 79, 50],
[53, 54, 66, 59, 38]])
In [253]: dup_cols(a, indx=2, num_dups=2)
Out[253]:
array([[19, 65, 87, 87, 87, 46, 85],
[18, 45, 90, 90, 90, 26, 31],
[49, 35, 34, 34, 34, 62, 24],
[47, 85, 63, 63, 63, 91, 33],
[54, 37, 89, 89, 89, 79, 50],
[53, 54, 66, 66, 66, 59, 38]])
Approach # 2
Another with np.repeat
-
In [102]: reps = np.ones(a.shape[0],dtype=int)
In [103]: reps[1] = 2 # duplication factor
In [104]: np.repeat(a,reps,axis=0)
Out[104]:
array([[0, 1, 2],
[3, 4, 5],
[3, 4, 5],
[6, 7, 8]])
+6
source to share