如何将字符串解析为实数方程 [英] How to parse a string into real equation

问题描述

我正在尝试将字符串转换为真实方程式.例如:我当前的字符串是

I am trying to convert a string into a real equation. For example: my current string is

> a<-"y = 31.563 + 5.923*x1 + 5.061*x2 - 0.662*x3 - 0.381*x4"
> class(a)
[1] "character"

现在，我有一个新的数据集:

Right now, I have a new data set:

x1=3 
x2=3
x3=4
x4=7
df_new = data.frame(x1,x2,x3,x4)

我想根据等式获得 y 的值.因此，我需要将该字符串转换为实方程式.有人知道怎么做吗?

I would like to get the value of y based on the equation. So I need to convert that string into real equation. Does anybody know how to do that?

推荐答案

这可能不是不是的最佳方法，而是 eval(parse(...))将起作用:

This is probably not the best way to do this, but eval(parse(...)) will work:

a <- "y = 31.563 + 5.923*x1 + 5.061*x2 - 0.662*x3 - 0.381*x4"
df_new <- data.frame(x1=3,x2=3,x3=4,x4=7)
eval(parse(text=gsub("y =","",a)),df_new)

我不太确定如何从 eval()返回的值，所以我摆脱了 y = 部分...

I wasn't quite sure how to get the value returned from eval() so I got rid of the y= part ...

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