如何计算两列的点积(将整列视为向量)? [英] How to compute the dot product of two column (think full column as a vector)?

问题描述

给了这张桌子:

| a | b |  c | 
|---+---+----+
| 3 | 4 |    |
| 1 | 2 |    |
| 1 | 3 |    |
| 2 | 2 |    |

我想得到两列 a 和 b 的点积，结果应该等于 (3*4)+(1*2)+(1*3)+(2*2)，即 21.

I want to get the dot product of two column a and b ,the result should be equel to (3*4)+(1*2)+(1*3)+(2*2) which is 21.

我不想使用笨拙的公式(B1*B2+C1*C2+D1*D2+E1*E2) 因为实际上我有一张大表等待计算.

I don't want use the clumsy formula (B1*B2+C1*C2+D1*D2+E1*E2) because actually I have a large table waiting to calculate.

我知道 emacs 的 Calc 工具有一个vprod"函数可以做这些事情，但我不知道如何将整列转换为向量.

I know emacs's Calc tool has a "vprod" function which can do those sort of things ,but I dont' know how to turn the full column to a vector.

谁能告诉我如何完成这项任务，感激不尽！

Can anybody tell me how to achieve this task,appreciate it!

推荐答案

在 emacs-calc 中，2 个向量的简单乘积计算点积.

In emacs-calc, the simple product of 2 vectors calculates the dot product.

这是有效的(我把结果放在 @6$3 中；括号也可以省略):

This works (I put the result in @6$3; also the parenthesis can be omitted):

| a | b | c  |
|---+---+----|
| 3 | 4 |    |
| 1 | 2 |    |
| 1 | 3 |    |
| 2 | 2 |    |
|---+---+----|
|   |   | 21 |
#+TBLFM: @6$3=(@I$1..@II$1)*(@I$2..@II$2)

@I 和 @II 从第一行到第二行.

@I and @II span from the 1st hline to the second.

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