CODEWITHSUNDEEP
rregression
Kate Lloyd
Kate Lloyd

Reputation: 31

Abline won't appear in R

I have run regression in R, when trying to fit an abline to the plot nothing happens, no error message appears.

I've had to log transform the data so I'm wondering if this is the issue? The data is not normally distributed however we have still been asked to perform regression.

Here is what I've tried so far:

alldata<-read.csv(file.choose(),header=T)

attach(alldata)

plot(weight.g,wingspan.mm,log="xy")

abline(lm(wingspan.mm~weight.g))

fit1<-lm(wingspan.mm~weight.g)

> summary(fit1)

fit2<-lm(log(wingspan.mm)~log(weight.g))

plot(fit2)

plot(weight.g,wingspan.mm,log="xy")

abline(fit2)

abline(lm(log(wingspan.mm)~log(weight.g)))

Can anyone spot where I am going wrong?

Thanks, Kate

Upvotes: 3

Views: 5036

Answers (1)

nico
nico

Reputation: 51640

abline won't plot a regression line over a log-transformed plot.

For instance this will only plot the points and not the regression line

plot(speed~dist, cars, log="xy")
abline(lm(speed~dist, cars))

To get around the problem use the untf parameter

plot(speed~dist, cars, log="xy")
abline(lm(speed~dist, cars), untf=T)

From ?abline:

If untf is true, and one or both axes are log-transformed, then a curve is drawn corresponding to a line in original coordinates, otherwise a line is drawn in the transformed coordinate system

Upvotes: 5

Related Questions