在ggplot2中，coord_flip和自由缩放不能一起使用

Question

Here is some example data for a hypothetical meta-analysis on the effectiveness of sports-promotion interventions for which I would like to create a forest plot:

example.df = data.frame(Author = c("McAuliffe et al.", "Palen et al.", "Manning et al.", "Richters et al.", "Grello et al.","Mpofu et al.", "Kuo & St Lawrence", "Langstrom & Hanson", "Ompad et al.", "Abdullah et al.","Yan", "Peltzer & Pengpid", "Lo & Wei", "Haggstrom-Nordin et al.", "Mwaba & Naidoo", "Hughes et al.","Lydie et al.", "Zimmer-Gembeck et al.", "Babalola", "Garos et al.", "Pinkerton et al."),
                    Sport = c("Basketball", "Basketball", "Baseball", "Dance", "Baseball", "Dance", "Wrestling","Wrestling", "Dance", "Baseball", "Wrestling", "Dance", "Swimming", "Swimming","Basketball", "Basketball", "Basketball", "Basketball", "Basketball", "Swimming", "Wrestling"),
                    Gender = c("Male", "Female", "Male", "Male", "Female", "Male", "Male", "Male", "Male", "Female","Female", "Male", "Female", "Female", "Female", "Male", "Female", "Female", "Female", "Male", "Female"),
                    d = c(-0.12, 0.53, 0.11, 0.02, 0.32, 0.04, 0.03,0.04,0.26, 0.76, 1.11, 0.34, 0.77, 1.19, 0.59, 0.15, 0.30, 0.81, 0.12, 0.11, 1.01),
                    d_SE = c(.10, .04, .06, .01, .11, .08, .08, .04, .05, .05, .14, .07, .05, .08, .19, .16, .07, .16, .06, .18, .15))

The data frame contains author names, the sport, whether the sample was male or female, the effect size for the intervention, and the standard error of the effect size. I am hoping to create a dot plot mapping shape to gender, and faceting by the particular sport. After following examples in Chang's "cookbook" and this related query , I've come up with the following code that meets most of my formatting needs:

p<-ggplot(example.df, aes(x=Author, y=d, ymin=d-1.96*d_SE, ymax=d+1.96*d_SE,shape=Gender))+ 
geom_pointrange() + 
coord_flip()+
scale_y_continuous(limits=c(-2,2),breaks=c(-2,-1.5,-1,-0.5,0,.5,1,1.5,2))+
geom_hline(yintercept=0, color="grey60",linetype="dashed")+
theme_bw()+
theme(panel.grid.major.x=element_blank(),panel.grid.minor.x=element_blank(),panel.grid.major.y=element_line(color="grey60",linetype="dashed"))+
facet_grid(Sport ~ ., scales="free_y")
p

My problem, however, is that the resulting plots for each facet (below) have every author in the entire data frame plotted on the y-axis (technically x-axis, but the axes are flipped). Instead, I only want the authors with data relevant to a given facet to be plotted on the author-associated axis of that facet, so each facet should have a different list of authors on the axis.

I had thought the scales="free_y" component of the facet_grid layer would ensure a unique author axis for each facet (I've also tried scales="free_x" , given the inverted axes), but this is not having the intended effect.

Does anyone know of a way that I could ensure that the only author names that appear on each facet's axis are the ones with associated data for that facet?

Answer 1

Andrie's right, in that coord_flip() seems to be the root of the issue. However, the convention for forest plot formatting is to have the author names on y-axis, so I wanted to find a way that still would meet this formatting requirement.

The accepted answer in the post that Gregor commented on actually solves my issue; the only required change was that I had to calculate columns for upper-bound/lower-bound values of the confidence intervals.

So now with the updated data frame:

example.df = data.frame(Author = c("McAuliffe et al.", "Palen et al.", "Manning et al.", "Richters et al.", "Grello et al.","Mpofu et al.", "Kuo & St Lawrence", "Langstrom & Hanson", "Ompad et al.", "Abdullah et al.","Yan", "Peltzer & Pengpid", "Lo & Wei", "Haggstrom-Nordin et al.", "Mwaba & Naidoo", "Hughes et al.","Lydie et al.", "Zimmer-Gembeck et al.", "Babalola", "Garos et al.", "Pinkerton et al."),
                    Sport = c("Basketball", "Basketball", "Baseball", "Dance", "Baseball", "Dance", "Wrestling","Wrestling", "Dance", "Baseball", "Wrestling", "Dance", "Swimming", "Swimming","Basketball", "Basketball", "Basketball", "Basketball", "Basketball", "Swimming", "Wrestling"),
                    Gender = c("Male", "Female", "Male", "Male", "Female", "Male", "Male", "Male", "Male", "Female","Female", "Male", "Female", "Female", "Female", "Male", "Female", "Female", "Female", "Male", "Female"),
                    d = c(-0.12, 0.53, 0.11, 0.02, 0.32, 0.04, 0.03,0.04,0.26, 0.76, 1.11, 0.34, 0.77, 1.19, 0.59, 0.15, 0.30, 0.81, 0.12, 0.11, 1.01),
                    d_SE = c(.10, .04, .06, .01, .11, .08, .08, .04, .05, .05, .14, .07, .05, .08, .19, .16, .07, .16, .06, .18, .15),
                    ci.low = c(-.30, .45, .00, -.01, .11, -.12, -.14, -.04, .16, .66, .84, .19, .68, 1.03, .22, -.17, .17, .50, .00, -.23, .72),
                    ci.high = c(.07, .62, .22, .05, .53, .20, .19, .11, .36, .87, 1.38, .47, .86, 1.35, .97,.47, .43, 1.11, .24, .46, 1.30))

#reorder Author based on value of d, so effect sizes can be plotted in descending order
example.df$Author<-reorder(example.df$Author, example.df$d, FUN=mean)

...and then for the plot (without any coord_flip() usage):

p <- ggplot(example.df, aes(y = Author, x = d, xmin = ci.low, xmax = ci.high, shape=Gender)) +
geom_point() +
geom_errorbarh(height = .1) +
scale_x_continuous(limits=c(-2,2),breaks=c(-2,-1.5,-1,-0.5,0,.5,1,1.5,2))+
geom_vline(xintercept=0, color="grey60",linetype="dashed")+
facet_grid(Sport ~ ., scales = "free", space = "free") +
theme_bw() +
theme(strip.text.y = element_text(angle = 0))
p

Very nice--thanks for all the suggestions and help troubleshooting this plot!

Answer 2

It seems that coord_flip() and free scales in the facets don't work well together. This is a known issue ( number 95 in the ggplot2 issue log ) and indications are that the fix is a huge rewrite and will not be done soon. Hadley says:

Free scales aren't going to be working with non-Cartesian coordinates systems for a long time :/

This means your only workaround may be to remove the coord_flip() . For example:

Try this:

library(ggplot2)
ggplot(example.df, aes(x=Author, y=d, ymin=d-1.96*d_SE, ymax=d+1.96*d_SE, shape=Gender, col=Gender))+ 
  geom_pointrange() + 
#   coord_flip()+
  scale_y_continuous(limits=c(-2,2),breaks=c(-2,-1.5,-1,-0.5,0,.5,1,1.5,2))+
  theme_bw()+
  theme(
    panel.grid.major.x=element_blank(),
    panel.grid.minor.x=element_blank(),
    axis.text.x = element_text(angle=90, hjust=1)
    ) +
  facet_grid(. ~ Sport, scales="free_x", space="free_x", shrink=TRUE, drop=TRUE)