本文介绍了给定索引处的numpy数组总和的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我要添加向量的值:
a = np.array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], dtype='d')到另一个向量的值:
c = np.array([10, 10, 10], dtype='d')位于另一个数组(大小为a,值为0 <= b[i] < len(c))给出的另一个数组
at position given by another array (of the same size of a, with values 0 <= b[i] < len(c))
b = np.array([2, 0, 1, 0, 2, 0, 1, 1, 0, 2], dtype='int32')这很容易用伪代码编写:
This is very simple to write in pseudo code:
for I in range(b.shape[0]): J = b[I] c[J] += a[I]类似的事情,但是矢量化了(c的长度实际上是几百个).
Something like this, but vectorized (length of c is some hundreds in real case).
c[0] += np.sum(a[b==0]) # 27 (10 + 1 + 3 + 5 + 8) c[1] += np.sum(a[b==1]) # 25 (10 + 2 + 6 + 7) c[2] += np.sum(a[b==2]) # 23 (10 + 0 + 4 + 9)我最初的猜测是:
c[b] += a,但仅将a的最后一个值相加.
but only last values of a are summed.
推荐答案您可以使用 np.bincount 以获得基于ID的加权总和,然后与c相加,就像这样-
You can use np.bincount to get ID based weighted summations and then add with c, like so -
np.bincount(b,a) + c更多推荐
给定索引处的numpy数组总和
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