Plotting a regression line through the origin

Question

I am plotting some data series along with regression lines using this code:

ggplot(dt1.melt, aes(x=lower, y=value, group=variable, colour=variable)) +
    geom_point(shape=1) +    
    geom_smooth(method=lm,  
            se=FALSE)   

However, I need to constrain the regression line to be through the origin for all series - in the same way as abline(lm(Q75~-1+lower,data=dt1)) would achieve on a standard R plot.

Can anyone explain how to do this in ggplot ?

Answer 1

You need to specify this in the formula argument to geom_smooth:

... + geom_smooth(method=lm, se=FALSE, formula=y~x-1)