R ggplot Plot from data in one data frame, label axis ticks using data frame a different data frame?

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I have 2 data sets. In data, b is encoded as numeric values. data1 represents the original in which b is chr data.

I would like to plot a box plot using the numeric data from data but pull the y-axis tick labels from the chr data b in data1. Is this possible?

Toy data:

data <- data.frame(a = c(1,1,1,1,1,2,2,2,2,2,3,3,3,3,3),
                   b = c(10,10,11,11,12,12,12,13,13,13,14,14,14,15,15),
                   c = c('x','y','y','x','y','y','x','y','y','x','y','y','x','x','y'))

data1 <- data.frame(a = c(1,1,1,1,1,2,2,2,2,2,3,3,3,3,3),
                   b = c('never','never','rare','rare','some','some','some','most','most','most','often','often','often','always','always'),
                   c = c('x','y','y','x','y','y','x','y','y','x','y','y','x','x','y'))

My attempt to achieve the outcome using scale_y_discrete:

ggplot(data,aes(x = as.factor(a), y = b, fill = c))+
      geom_boxplot()+
  scale_y_discrete(data1$b,labels=unique(data1$b))

enter image description here

As you can see, the y-axis tick labels are not displaying as anticipated.

For further reference, this is to be used on a far larger data set as part of a Shiny application. The plot forms a reactive element and so I need to avoid hard-coding the actual label names.

Your help is appreciated.

ggplot2 r
1 Answers

As your b variable is continuous you have to use scale_y_continuous. While for your example data scale_y_continuous(labels = unique(data1$b)) will work, personally I would suggest to use a named vector of labels which is less error prone and assigns labels to numeric values:

library(ggplot2)

labels <- unique(data1$b)
names(labels) <- 10:15

ggplot(data,aes(x = as.factor(a), y = b, fill = c))+
  geom_boxplot()+
  scale_y_continuous(labels = labels)

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