Python:剪掉numpy数组的外框

Question

我正在使用一个numpy数组来存储特定区域的气候数据。该数组具有以下大小:

data.shape[0]=365, data.shape[1]=466 #y,x

假设我想通过剪切 data 的外框来创建一个新数组，例如消除 width=5 外框中的值。新数组将具有以下尺寸:

new.shape[0]=355, new.shape[1]=456 #y,x

我当前的数组采用以下形式:

array([[  0.        ,   0.        ,   0.        , ...,   0.        ,
          0.        ,   0.        ],
       [  0.        ,   0.        ,   0.        , ...,   0.        ,
          0.        ,   0.        ],
       [  0.        ,   0.        ,   0.        , ...,   0.        ,
          0.        ,   0.        ],
       ..., 
       [ 17.00830078,   0.        ,   0.        , ...,  28.21435547,
         28.28242111,  28.33056641],
       [  0.        ,   0.        ,   0.        , ...,  28.25419998,
         28.32392502,  28.34052658],
       [  0.        ,   0.        ,   0.        , ...,  28.23759842,
         28.31396484,  28.36874962]], dtype=float32)

如何在 Python 中实现这一点？

Answer 1

就slice -

c = 5  # No. of elems to be cropped on either sides
cropped_out = a[c:-c,c:-c]

示例运行 -

In [212]: a
Out[212]: 
array([[2, 8, 4, 1, 4, 2, 0, 1, 6, 1],
       [4, 0, 2, 8, 0, 4, 4, 2, 6, 5],
       [5, 7, 6, 6, 6, 4, 6, 4, 1, 7],
       [6, 8, 2, 4, 3, 0, 3, 0, 2, 2],
       [6, 2, 5, 1, 1, 3, 7, 3, 3, 5],
       [4, 8, 4, 5, 6, 8, 6, 1, 0, 7],
       [7, 2, 8, 8, 6, 7, 3, 1, 7, 2]])

In [213]: c = 2 # No. of elems to be cropped on either sides

In [214]: a[c:-c,c:-c]
Out[214]: 
array([[6, 6, 6, 4, 6, 4],
       [2, 4, 3, 0, 3, 0],
       [5, 1, 1, 3, 7, 3]])