Boxplot Error "Must request at least one color from a hue palette"

[CEFC]

Hello,

I am very new to R and therefore I need some advices.
I want to plot a grouped Boxplots on one axis.
Therefore I used this code:

Run100.mw$Gender <- as.factor(Run100.mw$Gender)
Run100.mw$Gender <- factor(Run100.mw$Gender, levels=c(1,2), labels=c("Male", "Female"))
library(ggplot2)
ggplot(Run100.mw, aes(x= as.factor(YEAR), y = MARK, fill=Gender)) + geom_boxplot()

Unfortunately it returns this error code and I am not able to identify my mistake:

Must request at least one colour from a hue palette.

Thank you in advance for your support,

Kind regards
CEFC

[andresrcs]

Hi, welcome!

To help us help you, could you please prepare a reproducible example (reprex) illustrating your issue? Please have a look at this guide, to see how to create one:

FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A minimal reproducible example consists of the following items: A minimal dataset, necessary to reproduce the issue The minimal runnable code necessary to reproduce the issue, which can be run on the given dataset, and including the necessary information on the used packages. Let's quickly go over each one of these with examples: Minimal Dataset (Sample Data) You need to provide a data frame that is small enough to be (reasonably) pasted on a post, but big enough to reproduce your issue. Let's say, as an example, that you are working with the iris data frame head(iris) #> Sepal.Length Sepal.Width Petal.Length Petal.Width Species #> 1 5.1 3.5 1.4 0.…

[FJCC]

This reproduced your error. Note that Gender has only NA values. I suggest you look at the data frame content just before you plot the data. If this hint does not solve your problem, please make a reprex as requested by andresrcs.

Run100.mw <- data.frame(YEAR = rep(c(2018, 2019), 10),
                        Gender = rep(c("Male", "Male", "Female", "Female"), 5),
                        MARK = rnorm(20, 5, 1), stringsAsFactors = FALSE)
Run100.mw$Gender <- as.factor(Run100.mw$Gender)
Run100.mw$Gender <- factor(Run100.mw$Gender, levels=c(1,2), labels=c("Male", "Female"))

str(Run100.mw)
#> 'data.frame':    20 obs. of  3 variables:
#>  $ YEAR  : num  2018 2019 2018 2019 2018 ...
#>  $ Gender: Factor w/ 2 levels "Male","Female": NA NA NA NA NA NA NA NA NA NA ...
#>  $ MARK  : num  5.64 5.38 5.4 6.61 5.28 ...
library(ggplot2)
ggplot(Run100.mw, aes(x= as.factor(YEAR), y = MARK, fill=Gender)) + geom_boxplot()
#> Error: Must request at least one colour from a hue palette.

^{Created on 2019-06-25 by the reprex package (v0.2.1)}

[mara]

The problem here is that your fill is mapped to a variable that is entirely populated with NAs (see the output from when you run str(Run100.mw)). If you keep Gender as a character, or convert it to a factor, the code runs fine.

Run100.mw <- data.frame(
  YEAR = rep(c(2018, 2019), 10),
  Gender = rep(c("Male", "Male", "Female", "Female"), 5),
  MARK = rnorm(20, 5, 1), stringsAsFactors = FALSE
)

str(Run100.mw)
#> 'data.frame':    20 obs. of  3 variables:
#>  $ YEAR  : num  2018 2019 2018 2019 2018 ...
#>  $ Gender: chr  "Male" "Male" "Female" "Female" ...
#>  $ MARK  : num  4.96 3.96 5.74 5.98 5.23 ...

library(ggplot2)
ggplot(Run100.mw, aes(x = as.factor(YEAR), y = MARK, fill = Gender)) + 
  geom_boxplot()

Run100.mw$Gender <- as.factor(Run100.mw$Gender)
str(Run100.mw)
#> 'data.frame':    20 obs. of  3 variables:
#>  $ YEAR  : num  2018 2019 2018 2019 2018 ...
#>  $ Gender: Factor w/ 2 levels "Female","Male": 2 2 1 1 2 2 1 1 2 2 ...
#>  $ MARK  : num  4.96 3.96 5.74 5.98 5.23 ...

ggplot(Run100.mw, aes(x = as.factor(YEAR), y = MARK, fill = Gender)) + 
  geom_boxplot()

^{Created on 2019-06-25 by the reprex package (v0.3.0)}