[R] What does lm() output coefficient mean when it's been given a categorical predictor of string values?

David Winsemius dwinsemius at comcast.net
Tue Oct 4 18:18:38 CEST 2016

> On Oct 4, 2016, at 8:39 AM, mviljamaa <mviljamaa at kapsi.fi> wrote:
> I'm using lm() for a model that has a predictor that has two values {poika, tyttö} (boy and girl in Finnish).
> I make a model with this categorical variable:
> fit1 <- lm(dta$X.U.FEFF..mpist. ~ dta$sukup + dta$HISEI + dta$SES)
> and while the variable/vector is here named as dta$sukup, what lm() returns is a coefficient
> dta$sukuptyttö
>     -6.19756
> What does the added 'tyttö' in the variable mean? Does it mean that 'tyttö' has been interpreted as 1 and 'poika' as 0?


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David Winsemius
Alameda, CA, USA

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