把零排在负片之前？

Question

我有一些数据，我想排序，但这个方法使用numpy.lexsort排序（）

data = np.zeros(shape=(n,6))
# some routine that partially populates the table
index = np.lexsort((data[:,0],data[:,1]))
data = data[index] # sort

用于桌子上，如

-500    0.5 0.0 0.0 0.0 0.0
-400    0.6 0.0 0.0 0.0 0.0
0.0     0.0 0.0 0.0 0.0 0.0
0.0     0.0 0.0 0.0 0.0 0.0

返回数据，例如：

0.0     0.0 0.0 0.0 0.0 0.0
0.0     0.0 0.0 0.0 0.0 0.0
-500    0.5 0.0 0.0 0.0 0.0
-400    0.6 0.0 0.0 0.0 0.0

但这很奇怪，对吧？你知道吗

Answer 1

正如塞伯格所说，你所看到的并不是错误的。Lexsort按提供的最后一个键排序，然后按倒数第二个键排序，依此类推，这看起来可能有点落后。从docstring：

The last key in the sequence is used for the primary sort order, the second-to-last key for the secondary sort order, and so on. The keys argument must be a sequence of objects that can be converted to arrays of the same shape. If a 2D array is provided for the keys argument, it's rows are interpreted as the sorting keys and sorting is according to the last row, second last row etc.

考虑到这一点，您看到的是正确的排序，但您可能想做的是：

data = np.zeros(shape=(n,6))
# some routine that partially populates the table
index = np.lexsort((data[:,1],data[:,0]))
data = data[index] # sort