总和numpy ndarray与给定轴1的3d数组

Question

我有一个形状(2,3,3)的numpy ndarray,例如:

array([[[ 1,  2,  3],
    [ 4,  5,  6],
    [12, 34, 90]],

   [[ 4,  5,  6],
    [ 2,  5,  6],
    [ 7,  3,  4]]])

我在np.sum(在ndarray,轴= 1之上)迷路了,为什么答案是:

array([[17, 41, 99],
   [13, 13, 16]])

谢谢

Answer 1

轴是为具有多个维度的数组定义的.二维阵列具有两个相应的轴:第一个在行(轴0)上垂直向下运行,第二个轴在列(轴1)上水平运行.

设A为数组,然后在示例中,当轴为1时,添加[i,:,k].同样,对于轴0,添加[:,j,k],当轴为2时,添加[i,j,:].

 A = np.array([[[ 1,  2,  3],[ 4,  5,  6],
    [12, 34, 90]],
    [[ 4,  5,  6],[ 2,  5,  6],
    [ 7,  3,  4]]])


np.sum(A,axis = 0)
    array([[ 5,  7,  9],
           [ 6, 10, 12],
           [19, 37, 94]])
np.sum(A,axis = 1)
    array([[17, 41, 99],
                   [13, 13, 16]])
np.sum(A,axis = 2)
    array([[  6,  15, 136],
           [ 15,  13,  14]])