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

[Luigi Marongiu]

Thank you, facets are good but I was looking for something that could
merge everything in a single plot. I found that I could create an
additional column, say M (merge), that accommodates two parameters
into one, for instance, `a + A`, `a + B` etc. By grouping for M, I can
kind of stratify the data...

On Sun, Jun 8, 2025 at 6:03 PM Rui Barradas <ruipbarradas using sapo.pt> wrote:
>
> Às 07:21 de 08/06/2025, Luigi Marongiu escreveu:
> > 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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> > and provide commented, minimal, self-contained, reproducible code.
> Hello,
>
> You can use the 4th variable to define facets. Like this?
>
>
> ggplot(df, aes(x=x, y=y, colour=w)) +
>    geom_line(linewidth=2) +
>    facet_wrap(~ z, scales = "free_x") +
>    ggtitle("A+B")
>
>
> Hope this helps,
>
> Rui Barradas
>
>
>
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-- 
Best regards,
Luigi