[R] Interaction scatterplots in ggplot with multiple regression lines

[John Kane]

Some like this help?

mydata$modnew  <-  cut(mydata$moderator, 7)
ggplot(mydata, aes(x=predictor, y=outcome, color=modnew)) +
geom_point() + stat_smooth(method=lm, se=TRUE, fullrange=T)


John Kane
Kingston ON Canada


> -----Original Message-----
> From: dadrivr at gmail.com
> Sent: Wed, 26 Sep 2012 09:45:07 -0400
> To: r-help at r-project.org
> Subject: [R] Interaction scatterplots in ggplot with multiple regression
> lines
> 
> I'm trying to treat a continuous variable as discrete for plotting
> multiple regression lines in a scatterplot as a function of the level
> on the moderating variable.  In the example below, there is only one
> regression line plotted to the whole data.  I would like a separate
> regression line for each discrete level of the moderator.  The
> moderator is continuous, so I'd like to treat it as discrete for
> plotting the regression lines.
> 
> Here's an example (I would like 7 regression lines corresponding to
> the discrete levels of the moderator, as displayed in the legend,
> instead of just 1 regression line):
> 
> ###########################
> library(ggplot2)
> set.seed(1234)
> predictor <- rnorm(1000, 3)
> outcome <- rnorm(1000, 10)
> moderator <- rnorm(1000)
> mydata <- data.frame(predictor, outcome, moderator)
> 
> ggplot(mydata, aes(x=predictor, y=outcome, color=moderator)) +
> geom_point() + scale_colour_gradient2(low="blue", high="red") +
> stat_smooth(method=lm, se=TRUE, fullrange=T)
> ###########################
> 
> Also, how can I set how many discrete levels to plot (e.g., 3 instead of
> 7)?
> 
> Thanks in advance!
> 
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