facet_wrap(nrow) ignored

Dear Ivan,

I don't think it is possible to force a number of rows - but I'm
honestly just guessing.

What you can do is to add an empty plot. Here I use cowplot, but
gridExtra should also work well.

I add an indication of the row number for the plot to the initial
data.frame, and loop over these.

In the first variant, I add an unused factor to the grp which creates
an empty facet. I personally think this looks a little confusing, so
in the second variant, I add a number of empty plots.

HTH
Ulrik

```
mydf <- data.frame(
? grp = rep(letters[1:6], each = 15),
? cat = rep(1:3, 30),
? var = rnorm(90),
? row_num = rep(c(1, 1, 2, 3, 4, 5), each = 15)
)

s_mydf <- split(mydf, mydf$row_num)

plots_mydf <- lapply(s_mydf, function(x){
? # Ensure no unused factors
? x$grp <- droplevels.factor(x$grp)
? if(length(unique(x$grp)) == 1){
??? x$grp <- factor(x$grp, levels = c(unique(x$grp), ""))
? }
? ggplot(data = x, aes(x = cat, y = var)) + geom_point() +
??? facet_wrap(~grp, drop=FALSE)
})

cowplot::plot_grid(plotlist = plots_mydf, nrow = 5)

# Maybe more elegant output
plots_mydf <- lapply(s_mydf, function(x, ncol = 2){
? # Ensure no unused factors
? x$grp <- droplevels.factor(x$grp)
? x <- split(x, x$grp)

? p <- lapply(x, function(x){
??? ggplot(data = x, aes(x = cat, y = var)) + geom_point() +
????? facet_wrap(~grp)
? })

? if(length(p) < ncol){
??? pe <- rep(list(ggplot() + theme_void()), ncol - length(p))
??? p <- c(p, pe)
? }
? cowplot::plot_grid(plotlist = p, ncol = ncol)
})

cowplot::plot_grid(plotlist = plots_mydf, ncol = 1)

# Or if you prefer not to split the plots on the same row
plots_mydf <- lapply(s_mydf, function(x, ncol = 2){

? p <- list(ggplot(data = x, aes(x = cat, y = var)) + geom_point() +
??? facet_wrap(~grp))

? if(length(unique(x$grp)) < ncol){
??? pe <- rep(list(ggplot() + theme_void()), ncol - length(p))
??? p <- c(p, pe)
? }else{
??? ncol <- 1
? }
? cowplot::plot_grid(plotlist = p, ncol = ncol)
})

cowplot::plot_grid(plotlist = plots_mydf, ncol = 1)

```

On 2020-09-09 17:30, Ivan Calandra wrote:

Dear useRs,

I have an issue with the argument nrow of ggplot2::facet_wrap().

Let's consider some sample data:
mydf <- data.frame(grp = rep(letters[1:6], each = 15), cat = rep(1:3,
30), var = rnorm(90))

And let's try to plot with 5 rows:
library(ggplot2)
ggplot(data = mydf, aes(x = cat, y = var)) + geom_point() +
facet_wrap(~grp, nrow = 5)
It plots 2 rows and 3 columns rather than 5 rows and 2 columns as
wanted.

These plots are as expected:
ggplot(data = mydf, aes(x = cat, y = var)) + geom_point() +
facet_wrap(~grp, nrow = 2)
ggplot(data = mydf, aes(x = cat, y = var)) + geom_point() +
facet_wrap(~grp, nrow = 6)

My guess is that 5 rows is not ideal for 6 facets (5 facets in 1st
column and only 1 facet for 2nd column) so it overrides the value of
nrow. In the case of 2 or 6 rows, the facets are well distributed in the
layout.

The reason why I need 5 rows with 6 facets is that this facet plot is
part of a patchwork and I would like to have the same number of rows for
all facet plots of the patchwork (so that they all align well).

Is there a way to force the number of rows in the facet_wrap()?

Thank you in advance.
Best,
Ivan

-- 


-- 
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
https://www.researchgate.net/profile/Ivan_Calandra