Grouping data for boxplot by month (and plotting chronologically)

Question

Let's say I have a 3 variables that were collected over 2 years

Var1 <- c(1:20)
Var2 <- c(41:60)
Var3<-c(81:100)
Date<- sample(seq(as.Date('2000/01/01'), as.Date('2002/12/31'), by="day"), 60)
data<-data.frame(Var1,Var2,Var3,Date)

I could like to create boxplots for each variable, combining by month, then plotting the months chronologically (Jan-Dec).

Right now my code looks like

boxplot(data$Var1 ~ reorder(format(data$Date,'%b %y'),data$Date))

or

boxplot(data$Var1~months(data$Date))

this gives me the full two years in chronological order, rather than just Months, or the months but in alphabetical order. Hope that makes sense! I am new to R but am learning ggplot as well.

Why do you not change the values in column *Date* to include only the month, but not the year, e.g. with the *substr* function? — cdalitz, Nov 26 '20 at 15:05
I can extract the months from the dates, but then I have the problem that they plot alphabetically, not chronologically — Gabrielle Macklin, Nov 26 '20 at 15:31
@GabrielleMacklin your question needs reproducible data, make sure you read https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example — Werner Hertzog, Nov 26 '20 at 15:39
Okay I edited to hopefully make it easier with some example data — Gabrielle Macklin, Nov 26 '20 at 15:46

score 0 · Answer 1 · answered Nov 26 '20 at 23:11

You have to reorder the month names proberly:

library(dplyr)
library(forcats)

data2 <- 
  data %>% 
  mutate(
    month = format(Date, "%m"),
    label = format(Date, "%b"),
    label = fct_reorder(label, month, min)
  )
boxplot(data2$Var1 ~ data2$label)

Grouping data for boxplot by month (and plotting chronologically)

1 Answers1