r - How can I solve non-finite location and/or size for viewport error?

Question

Here is a simplified and testable example:

dataset <- data.frame(
  emp_month = c("January","March","April","May","December"),
  salary = c(623.3,515.2,611.0,729.0,843.25))

library(ggplot2)

ggplot(dataset)+
  geom_boxplot(aes(x = sort(factor(emp_month)), y = salary))+
  geom_point(aes( x = sort(factor(emp_month)), y=salary))+
  facet_grid(. ~ sort(factor(emp_month)),space = "free", scales="free",margins = T)

Error Description:

I can write this code

library(ggplot2)
MesDeConclusao =  factor(MesDeConclusao, levels = month.name)
MesDeConclusao = sort(MesDeConclusao)
ggplot(dataset)+
    geom_boxplot(aes(x = MesDeConclusao, y = Horas.Totais.PE))+
   geom_point(aes( x = MesDeConclusao, y=Horas.Totais.PE))+
facet_grid(. ~  MesDeConclusao,space = "free", scales="free",margins = T)

and get this as output:

In order to ordenate months chronologically, I used sort and factor:

library(ggplot2)
MesDeConclusao =  factor(MesDeConclusao, levels = month.name)
MesDeConclusao = sort(MesDeConclusao)
ggplot(dataset)+
    geom_boxplot(aes(x = sort(factor(MesDeConclusao, levels = month.name)), y = Horas.Totais.PE))+
   geom_point(aes( x = sort(factor(MesDeConclusao, levels = month.name)), y=Horas.Totais.PE))+
facet_grid(. ~  sort(factor(MesDeConclusao, levels = month.name)),space = "free", scales="free")

The result was:

However, if I add margins = T to facet_grid(. ~ sort(factor(MesDeConclusao, levels = month.name)),space = "free", scales="free", margins = T) as I had in the previous example I get this error message:

Error in grid.Call.graphics(C_setviewport,vp,TRUE): non-finite location and/or size for viewport Calls: FUN -> push.vp.viewport -> grid.Call.graphics Execution halted

Answer 1

I don't understand why sorting the factor levels inside the plot would be beneficial; this is best handled before plotting the data. The following seems to work just fine for me:

# Just to ensure levels are in correct order
dataset$emp_month <- factor(
  dataset$emp_month, 
  levels = c("January", "March", "April", "May", "December")
  )

ggplot(dataset) +
  geom_boxplot(aes(x = emp_month, y = salary)) +
  geom_point(aes(x = emp_month, y = salary)) +
  facet_grid(. ~ emp_month ,space = "free", scales = "free", margins = T)