与 ~(在公式中)一起使用时，句点是什么意思? [英] What does the period mean when used with ~ (in a formula)?

问题描述

来自 FSelector 手册:

data(iris)
subset <- cfs(Species~., iris)
f <- as.simple.formula(subset, "Species")
print(f)

具体来说，我指的是物种~"中的那个.

Specifically, I mean the one in "Species~.".

现在，Google 很难使用标点符号(无论如何对我来说)，而我什么也做不了.这段代码不清楚.

Now, it's awfully tough to Google how a bit of punctuation is used (for me anyway) and I couldn't anything. This code is unclear.

推荐答案

我认为您指的是 Species~. 中包含的句点，在这种情况下，这只是标准的 R 公式引用数据框中的所有其他变量"，而不是像Species ~ Variable1 + Variable2 等中那样将它们一个一个地键入.

I think you're referring to the period contained in Species~., in which case this is just the standard R formulation of referring to 'all other variables' in the data frame, rather than typing them out one by one, as in Species ~ Variable1 + Variable2 etc.

来自?formula的帮助文件:

有两种特殊的解释.在一个公式中.平时的在模型拟合函数的数据参数的上下文中，并且表示不在公式中的所有列":请参阅terms.formula.在 update.formula 的上下文中，仅表示以前是什么在公式的这一部分'.

There are two special interpretations of . in a formula. The usual one is in the context of a data argument of model fitting functions and means ‘all columns not otherwise in the formula’: see terms.formula. In the context of update.formula, only, it means ‘what was previously in this part of the formula’.

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