What does the full stop do when assigned to a formula in r? In the parameter of lm

Question

I am a C# developer, new to R, trying to understand the code line

fit <- lm(quality ~ .,wine)

I get that this creates a list called fit and that

quality ~ .

must somehow instantiate an object of class "formula" for use within the lm function.

from typing

help("~")

into the R Studio Console, I see that

Tilde is used to separate the left- and right-hand sides in a model formula.
Usage y ~ model
Arguments y, model symbolic expressions.
Details The left-hand side is optional, and one-sided formulae are used in some contexts.

A formula has mode call. It can be subsetted by [[: the components are ~, the left-hand side (if present) and the right-hand side in that order.

But I am not told what the left and right sides in a model formula are.

What does the following mean?

quality ~ .

What is meant by

the left and right hand sides

of a model formula?

Thanks, I added to the question. – Kirsten Oct 29 '20 at 23:48 — Kirsten, Oct 29 '20 at 23:48

akrun · Accepted Answer · 2020-10-30T00:07:52.523

1

As this is concerned with formula, we can check the documentation of ?formula

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’.

edited Oct 30 '20 at 00:07

answered Oct 29 '20 at 23:48

akrun

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Thanks, is there any way to enlarge the Help Window in RStudio? I am having trouble locating the update context – Kirsten Oct 29 '20 at 23:55
Ah, where are you typing "?formula " ? – Kirsten Oct 30 '20 at 00:06
@KirstenGreed it is in the console – akrun Oct 30 '20 at 00:07
@KirstenGreed I generally use R console. Just to show where you could use it in Rstudio, I updated with a screenshot – akrun Oct 30 '20 at 00:08
Thanks. RConsole looks very similar to RStudio – Kirsten Oct 30 '20 at 00:11
@KirstenGreed that is Rstudio. I meant that I don't generally use Rstudio – akrun Oct 30 '20 at 00:12

What does the full stop do when assigned to a formula in r? In the parameter of lm

1 Answers1