Dear useRs:
I am having difficulty understanding how to make a legend in ggplot when I only
want certain geoms to be indicated, in the presence of nested groups. An
example:
require(tidyverse)
dat <- tibble(X=rep(seq(4),3),
# fake data
Y=c(-1.11, -0.46, 0.02, 0.81,
-0.51, 0.43, 0.73, 1.39,
-0.12, 0.62, 1.19, 1.99
),
G1=rep(seq(3), each=4) %>% factor)
dat <- dat %>% mutate(lin=predict(lm(Y~X*G1, dat)),
quad=predict(lm(Y~poly(X,2)*G1, dat)))
Now dat contains one grouping variable, G1, the X and Y data, and two columns
of fitted values. I want to consolidate the fitted value columns for plotting:
# stack model fits: make wide -> long
dat <- dat %>% gather(lin:quad, key="Model", value="fit", factor_key=TRUE)
Thus the model variable acts as another grouping variable.
I want to plot the two fits over the raw data, with the raw data grouped and
annotated by G1, and the fits grouped by model*G1 but annotated by only model.
Thus each G1 will have separately annotated model fits plotted, but the same
model annotations will be the same for all levels of G1. Here is the code that
I thought would do this.
# init plot
pl <- ggplot(data=dat, mapping=aes(x=X, y=Y, group=interaction(Model,G1))) +
theme_bw()
# add raw data in background
pl <- pl +
geom_path(data=dat %>% filter(Model=='lin'), # filter probably not
necessary but prevents redundant overplotting
mapping=aes(x=X, y=Y, group=G1, color=G1), linetype=2,
show.legend=FALSE) +
geom_point(data=dat %>% filter(Model=='lin'),
mapping=aes(x=X, y=Y, group=G1, color=G1, shape=G1),
show.legend=FALSE)
# add fits
pl <- pl + geom_path(aes(x=X, y=fit, group=interaction(Model,G1),
color=Model) )
pl
The plot looks as I want it. But the legend is titled G1, and has the levels
of G1 in the legend (as well as the desired Model levels). But I thought
turning off the show.legend argument in the raw data geoms would prevent this.
What I desire in the legend is only the two levels of Model (and titled as
such).
Any assistance greatly appreciated.
John
John Szumiloski, Ph.D.
Principal Scientist, Statistician
Pharmaceutical Development / Analytical and Bioanalytical
Operations<http://teams.bms.com/sites/ARD/>
NBR105-1-1411
Bristol-Myers Squibb
P.O. Box 191
1 Squibb Drive
New Brunswick, NJ
08903-0191
(732) 227-7167
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