numpy的squeeze函数

http://blog.csdn.net/zenghaitao0128/article/details/78512715

reshape函数：改变数组的维数（注意不是shape大小）

>>> e= np.arange(10)
>>> e
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

>>> e.reshape(1,1,10)

array([[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]])

>>> e.reshape(1,1,10)
array([[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]])
>>> e.reshape(1,10,1)
array([[[0],
        [1],
        [2],
        [3],
        [4],
        [5],
        [6],
        [7],
        [8],
        [9]]])

squeeze 函数：从数组的形状中删除单维度条目，即把shape中为1的维度去掉

用法：numpy.squeeze(a,axis = None)

 1）a表示输入的数组；
 2）axis用于指定需要删除的维度，但是指定的维度必须为单维度，否则将会报错；
 3）axis的取值可为None 或 int 或 tuple of ints, 可选。若axis为空，则删除所有单维度的条目；
 4）返回值：数组
 5) 不会修改原数组；

>>> a = e.reshape(1,1,10)
>>> a
array([[[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]]])
>>> np.squeeze(a)
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

体现在画图时

>>> plt.plot(a)
Traceback (most recent call last):
  File "", line 1, in 
  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 3240, in plot
    ret = ax.plot(*args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\__init__.py", line 1710, in inner
    return func(ax, *args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\axes\_axes.py", line 1437, in plot
    for line in self._get_lines(*args, **kwargs):
  File "C:\Python27\lib\site-packages\matplotlib\axes\_base.py", line 404, in _grab_next_args
    for seg in self._plot_args(this, kwargs):
  File "C:\Python27\lib\site-packages\matplotlib\axes\_base.py", line 384, in _plot_args
    x, y = self._xy_from_xy(x, y)
  File "C:\Python27\lib\site-packages\matplotlib\axes\_base.py", line 246, in _xy_from_xy
    "shapes {} and {}".format(x.shape, y.shape))
ValueError: x and y can be no greater than 2-D, but have shapes (1L,) and (1L, 1L, 10L)
>>> plt.plot(np.squeeze(a))
[]
>>> plt.show()

>>> np.squeeze(a).shape
(10L,)

通过np.squeeze()函数转换后，要显示的数组变成了秩为1的数组，即（10，）

参考：http://blog.csdn.net/zenghaitao0128/article/details/78512715