Why does facet_grid work, but not facet_wrap?

Question

I would like to use faceting, but also to control the number of rows and columns. So facet_wrap is preferred to facet_grid. But while facet_grid works, facet_wrap does not and gives an error: "At least one layer must contain all variables used for facetting". Why does this occur? How can I use facet_wrap here?

x <- rnorm(8)
y <- x + rnorm(8, sd=0.7)
dd <- data.frame(id=rep(1:4, 2), x=x, y=y)
pp <- ggplot(dd, aes(x, y)) + geom_point()
pp  
pp + facet_grid(. ~ id)  # works
pp + facet_wrap(. ~ id)  # error

...to expand, `facet_wrap` "wraps" a 1D set of facets into a grid, so the formula should really just be one sided. For multiple variables, you'd do `facet_wrap(~ id + var)`. — joran, Feb 20 '14 at 17:18
Fought with this for like 30 minutes. Thanks -- this answer solved my problem! — Alex Coppock, Jan 28 '15 at 04:13
@boethian, please add the above as an answer and have the question closed. — Eric Fail, Jan 10 '16 at 23:31

score 19 · Accepted Answer · answered Jan 12 '16 at 00:24

19

Drop the . in facet_wrap because the formula is one-sided:

pp + facet_wrap(~ id)

answered Jan 12 '16 at 00:24

alexperrone

667
5
12

can you please take a look at my question? https://stackoverflow.com/questions/65676788/combining-different-types-of-graphs-together-r thanks – stats_noob Jan 12 '21 at 02:04

Why does facet_grid work, but not facet_wrap?

1 Answers1