[英]Filling zeros in numpy array that are between non-zero elements with the same value
我有一个带整数的一维numpy numpy数组,当且仅当下一个非零值相同时,我才想用先前的非零值替换零。
例如,一个数组:
in: x = np.array([1,0,1,1,0,0,2,0,3,0,0,0,3,1,0,1])
out: [1,0,1,1,0,0,2,0,3,0,0,0,3,1,0,1]
应该成为
out: [1,1,1,1,0,0,2,0,3,3,3,3,3,1,1,1]
有矢量化的方法可以做到这一点吗? 我在这里找到了一种填充零值的方法,但是没有找到例外的方法,即不填充具有不同值的整数内的零。
这是一种矢量化方法,该方法从NumPy based forward-filling
方法中获取此解决方案中的正向填充部分以及masking
和slicing
灵感-
def forward_fill_ifsame(x):
# Get mask of non-zeros and then use it to forward-filled indices
mask = x!=0
idx = np.where(mask,np.arange(len(x)),0)
np.maximum.accumulate(idx,axis=0, out=idx)
# Now we need to work on the additional requirement of filling only
# if the previous and next ones being same
# Store a copy as we need to work and change input data
x1 = x.copy()
# Get non-zero elements
xm = x1[mask]
# Off the selected elements, we need to assign zeros to the previous places
# that don't have their correspnding next ones different
xm[:-1][xm[1:] != xm[:-1]] = 0
# Assign the valid ones to x1. Invalid ones become zero.
x1[mask] = xm
# Use idx for indexing to do the forward filling
out = x1[idx]
# For the invalid ones, keep the previous masked elements
out[mask] = x[mask]
return out
样品运行-
In [289]: x = np.array([1,0,1,1,0,0,2,0,3,0,0,0,3,1,0,1])
In [290]: np.vstack((x, forward_fill_ifsame(x)))
Out[290]:
array([[1, 0, 1, 1, 0, 0, 2, 0, 3, 0, 0, 0, 3, 1, 0, 1],
[1, 1, 1, 1, 0, 0, 2, 0, 3, 3, 3, 3, 3, 1, 1, 1]])
In [291]: x = np.array([1,0,1,1,0,0,2,0,3,0,0,0,1,1,0,1])
In [292]: np.vstack((x, forward_fill_ifsame(x)))
Out[292]:
array([[1, 0, 1, 1, 0, 0, 2, 0, 3, 0, 0, 0, 1, 1, 0, 1],
[1, 1, 1, 1, 0, 0, 2, 0, 3, 0, 0, 0, 1, 1, 1, 1]])
In [293]: x = np.array([1,0,1,1,0,0,2,0,3,0,0,0,1,1,0,2])
In [294]: np.vstack((x, forward_fill_ifsame(x)))
Out[294]:
array([[1, 0, 1, 1, 0, 0, 2, 0, 3, 0, 0, 0, 1, 1, 0, 2],
[1, 1, 1, 1, 0, 0, 2, 0, 3, 0, 0, 0, 1, 1, 0, 2]])
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