numpy - 将未知大小的 2-D 数组组合起来形成一个 3-D

Question

我有一个函数，比如 PeaksDetect()，它将生成一个未知行数的二维数组；我会调用它几次，假设是 3 次，我想将这 3 个数组组成一个 3-D 数组。这是我的开始，但它非常复杂，有很多 if 语句，所以我想让事情尽可能简单:

import numpy as np

dim3 = 3   # the number of times peaksdetect() will be called
           # it is named dim3 because this number will determine 
           # the size of the third dimension of the result 3-D array

for num in range(dim3):
    data = peaksdetect(dataset[num])            # generates a 2-D array of unknown number of rows
    if num == 0:
        3Darray = np.zeros([dim3, data.shape])  # in fact the new dimension is in position 0
                                                # so dimensions 0 and 1 of "data" will be 
                                                # 1 and 2 respectively
    else:
        if data.shape[0] > 3Darray.shape[1]:
            "adjust 3Darray.shape[1] so that it equals data[0] by filling with zeroes"
            3Darray[num] = data
        else:
            "adjust data[0] so that it equals 3Darray.shape[1] by filling with zeroes"
            3Darray[num] = data
...

Answer 1

如果您指望必须调整数组大小，那么预分配它很可能不会获得太多好处。将数组存储在列表中可能会更简单，然后计算出容纳所有数组的数组大小，并将数据转储到其中:

data = []
for num in range(dim3):
    data.append(peaksdetect(dataset[num]))
shape = map(max, zip(*(j.shape for j in data)))
shape = (dim3,) + tuple(shape)
data_array = np.zeros(shape, dtype=data[0].dtype)
for j, d in enumerate(data):
    data_array[j, :d.shape[0], :d.shape[1]] = d