[R] Problem in overlying two figures in ggplot2

[Ista Zahn]

Hi Kristi,

There is a separate ggplot2 mailing list at
https://groups.google.com/forum/#!forum/ggplot2, please post future
ggplot2 questions there.

On Mon, Jan 27, 2014 at 11:52 AM, Kristi Glover
<kristi.glover at hotmail.com> wrote:
> Hi R Users,
> I was struggling to overlay two graphs created from the two different datasets using ggplot2.I could not overlay two figures. I wanted to plot second graph using second Y axis. but there was no provision.
> Furthermore, I could not join means of the box plots.
>
> I tried this way but did not work. Any suggestions?
> dat1<-structure(list(site = c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L,
> 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L), layer = structure(c(2L,
> 2L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 1L, 2L, 2L, 2L, 1L, 1L,
> 1L, 1L), .Label = c("bottom", "top"), class = "factor"), Present = c(120L,
> 125L, 123L, 23L, 21L, 19L, 131L, 124L, 127L, 24L, 27L, 25L, 145L,
> 143L, 184L, 29L, 14L, 17L, 38L)), .Names = c("site", "layer",
> "Present"), row.names = c(NA, 19L), class = "data.frame")
> dat1
> dat2<-structure(list(site = 1:3, present = c(-3L, 2L, 5L)), .Names = c("site",
> "present"), row.names = c(NA, 3L), class = "data.frame")
> dat2
> library("plyr")
> library(ggplot2)
> A<-ggplot(dat1, aes(x = factor(site), y = Present, colour = layer, fill=layer)) +
>     geom_boxplot(outlier.shape = 16, outlier.size = 1)  + theme_bw()+ ylim(0,185)
> # Here I wanted to join the means of the boxplots among the sites, but I could not join it.

It would have been useful to show us what you tried, but here is one way:

A + geom_line(aes(
    group = layer # ignore the fact that the x-axis is categorical
    ),
              position = position_dodge(width = 0.75), # match position of boxes
              stat="summary", # summarize raw data
              fun.y = mean, # by taking the mean
              color="black")

> B<-ggplot(dat2, aes(x=factor(site),y= present, colour="blue") +
>      geom_line() + geom_point()) # wanted to plot it using second y axis.

ggplot2 doesn't really support multiple y axes. You can fake it (check
the ggplot2 mailing list and/or stackoverflow for examples) but it's
not easy.

Best,
Ista

> A+B
> Thanks for your help.
> KG
>
>
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