How to plot logit and probit in ggplot2

Question

This is almost surely a newbish question/

For the dataset below I have been trying to plot both the logit and the probit curves in ggplot2 without success.

Answer 1

These two functions that you use in stat_smooth overlap. This is why you think you can't see those two on the same graph. Running the below will make this clear having a blue colour for the second line.

library(ggplot2)
TD<-mydata$TD
Temp<-mydata$Temp
g <- qplot(Temp,TD)+geom_point()+stat_smooth(method="glm",family="binomial",formula=y~x,col="red")
g1<-g+labs(x="Temperature",y="Thermal Distress")
g1
g2<-g1+stat_smooth(method="glm",family="binomial",link="probit",formula=y~x,add=T,col='blue')
g2

If you run a different family on the second stat_smooth, for example a poisson glm:

library(ggplot2)
TD<-mydata$TD
Temp<-mydata$Temp
g <- qplot(Temp,TD)+geom_point()+stat_smooth(method="glm",family="binomial",formula=y~x,col="red")
g1<-g+labs(x="Temperature",y="Thermal Distress")
g1
g2<-g1+stat_smooth(method="glm",family="poisson",link="log",formula=y~x,add=T,col='blue')
g2

Then you can see that indeed two lines are plotted: