python - lexsort 负数之前的零？

Question

我有一些数据想要排序，但此方法使用 numpy.lexsort()

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

用在 table 上，例如

-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？

Answer 1

正如塞伯格所说，您所看到的并不正确。 Lexsort 按提供的最后一个键排序，然后是倒数第二个键，依此类推，这可能看起来有点落后。从文档字符串:

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，您所看到的内容已正确排序，但您可能想要执行以下操作:

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