如何对每n个数组值求和并将结果放入新数组中? [英] How can I sum every n array values and place the result into a new array?

问题描述

我有一个很长的数组编号列表，我想对它们进行求和并放入一个新数组中.例如数组:

I have a very long list of array numbers I would like to sum and place into a new array. For example the array:

[1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8]

将成为:

[6,15,16,6,15,x]

如果我想每3加总一次.

if I was to sum every 3.

我不知道该怎么做.我认为可能的一个问题是我不知道我的数组的长度-如果有必要，我不介意丢失数据的最低位.

I cannot figure out how to go about it. I think possibly one problem is I do not know the length of my array - I do not mind losing the bottom bit of data if necessary.

我尝试了numpy.reshape函数，但没有成功:

I have tried the numpy.reshape function with no success:

x_ave = numpy.mean(x.reshape(-1,5), axis=1)

ret = umr_sum(arr, axis, dtype, out, keepdims)

我得到一个错误:

TypeError: cannot perform reduce with flexible type

推荐答案

首先将数组剪切为正确的长度，然后进行整形.

Cut the array to the correct length first then do a reshape.

import numpy as np

N = 3
a = np.array([1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8])


# first cut it so that lenght of a % N is zero
rest = a.shape[0]%N
a = a[:-rest]


assert a.shape[0]%N == 0


# do the reshape
a_RS = a.reshape(-1,N)
print(a_RS)

>> [[1 2 3]
    [4 5 6]
    [7 8 1]
    [2 3 4]
    [5 6 7]]

然后您可以简单地将其添加:

then you can simply add it up:

print(np.sum(a_RS,axis=1))

>> [ 6 15 16  9 18]

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