[R] How to stratify data with multiple group simultaneously with R ggplot2?

[Jeff Newmiller]

You can use group=interaction(w,z)... but in my experience that gets confusing for the poor person trying to make sense of the plot. It is better to use color=w, linetype=z or use facets for one of the grouping variables.

On June 7, 2025 11:21:32 PM PDT, Luigi Marongiu <marongiu.luigi using gmail.com> wrote:
>I would like to plot multivariate data with ggplot2. I have multiple
>groups that I need to account for: I have the `x` and `y` values, but
>the data must be stratified also by `w` and `z`. I can group by either
>`w` or `z`, but how can I group for both simultaneously?
>In essence, in the example below, the legend should have two columns
>(A and B) and five rows (which are already there since the data is
>stratified by w). There should be 10 colors.
>How can I do that?
>Thank you
>
>>>>>>>
>```
>df = data.frame(x = c(rep(1,5), rep(2,5), rep(3,5), rep(4,5)),
>                                w = rep(letters[1:5],4),
>                                z = c(rep(LETTERS[1],10), rep(LETTERS[2],10)),
>                                y = rnorm(20),
>                                stringsAsFactors = FALSE)
>library(ggplot2)
>ggplot(df, aes(x=x, y=y, colour=w, group=w)) +
>  geom_line(linewidth=2) +
>  ggtitle("A+B")
>ggplot(df[df$z=="A",], aes(x=x, y=y, colour=w, group=w)) +
>  geom_line(linewidth=2) +
>  ggtitle("A")
>ggplot(df[df$z=="B",], aes(x=x, y=y, colour=w, group=w)) +
>  geom_line(linewidth=2) +
>  ggtitle("B")
>```
>
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-- 
Sent from my phone. Please excuse my brevity.