在numpy数组中将所有零转换为介于1之间的零

Question

Consider a numpy array

arr = numpy.array([[1,0,1,0,1,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,1,1,1,1,1,1,1,1],
[1,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0,1],
[0,0,0,0,0,1,0,1,1,1,1,1,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0]])

I want convert all zeroes to ones between ones

output should be

[[1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1],
 [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1],
 [0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0]]

How can I achieve this? Is there any numpy function to achieve that?

Answer 1

Here's one approach using np.maximum.accumulate by using it on a column-flipped version and without it and simply getting the intersection of them -

def fill_gaps(arr):
    ma = np.maximum.accumulate
    return ma(arr[:,::-1],axis=1)[:,::-1] & ma(arr,axis=1)

Sample runs -

# Sample #1
In [27]: print arr
[[1 0 1 0 1 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 1 1 1 1 1 1 1]
 [1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1]
 [0 0 0 0 0 1 0 1 1 1 1 1 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0]]

In [28]: print fill_gaps(arr)
[[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0]]

# Sample #2
In [42]: print arr
[[1 0 1 0 1 0 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 1 1 1 1 1 1 1]
 [0 0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 0]
 [0 0 0 0 0 1 0 1 1 1 1 1 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0]]

In [43]: print fill_gaps(arr)
[[1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1]
 [0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0]
 [0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0]]

To fill for an array with 0s and some other value say 255s , here's a modification -

def fill_gaps(arr, value=1):
    ma = np.maximum.accumulate
    mask = arr==value
    mask_filled = ma(mask[:,::-1],axis=1)[:,::-1] & ma(mask,axis=1)
    return np.where(mask_filled,value,0)

Sample run -

In [69]: print arr
[[255   0 255   0 255   0 255   0   0   0   0 255   0   0   0   0   0   0
    0 255   0   0 255 255 255 255 255 255 255 255]
 [  0   0   0 255   0 255   0 255   0 255   0 255   0 255   0 255   0 255
    0 255   0 255   0 255   0 255   0 255   0   0]
 [  0   0   0   0   0 255   0 255 255 255 255 255   0   0   0 255 255 255
    0   0   0   0   0   0   0   0   0   0   0   0]]

In [70]: print fill_gaps(arr, 255)
[[255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
  255 255 255 255 255 255 255 255 255 255 255 255]
 [  0   0   0 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
  255 255 255 255 255 255 255 255 255 255   0   0]
 [  0   0   0   0   0 255 255 255 255 255 255 255 255 255 255 255 255 255
    0   0   0   0   0   0   0   0   0   0   0   0]]