I have a boxplot from the code below and i want to add median values.
boxplot(ndvi_pct_sep~edge_direction, data= data_sample, subset = edge_direction %in% c(64,4, 1,16),ylab="NDVI2028-2016", xlab="Forest edge direction",names=c("north", "south", "east", "west"))
. I want to add the median values to the boxplots, any idea how to do it?
It will likely involve using legends - since I don't have your data I cant make it perfect, but the below code should get you started using the ToothGrowth data contained in R. I am showing a base R and ggplot example (I know you said no ggplot, but others may use it).
# Load libraries
library(dplyr); library(ggplot2)
# get median data
mediandata <- ToothGrowth %>% group_by(dose) %>% summarise(median = median(len, na.rm = TRUE))
l <- unname(unlist(mediandata))
tg <- ToothGrowth # for convenience
tg$dose <- as.factor(tg$dose)
### Base R approach
boxplot(len ~ dose, data = tg,
main = "Guinea Pigs' Tooth Growth",
xlab = "Vitamin C dose mg",
ylab = "tooth length", col = "red")
for (i in 1:3){
legend(i-0.65,l[i+3]+5, legend = paste0("Median: ",l[i+3]), bty = "n")
}
### ggplot approach
ggplot(data = tg, aes(dose, len)) +
theme_classic() + theme(legend.position = "none") +
geom_boxplot()+
annotate("text",
x = c(1,2,3),
y = l[4:6]+1, # shit so you can read it
label = l[4:6])
Base R:
ggplot:
Here's a straightforward solution with text and without forloop:
Toy data:
set.seed(12)
df <- data.frame(
var1 = sample(LETTERS[1:4], 100, replace = TRUE),
var2 = rnorm(100)
)
Calculate the medians:
library(dplyr)
med <- df %>%
group_by(var1) %>%
summarise(medians = median(var2)) %>%
pull(medians)
Alternatively, in base R:
bx <- boxplot(df$var2 ~ df$var1)
med <- bx$stats[3,1:4]
Boxplot:
boxplot(df$var2 ~ df$var1)
Annotate boxplots:
text(1:4, med, round(med,3), pos = 3, cex = 0.6)
You can do
b <- boxplot(count ~ spray, data = InsectSprays, col = "lightgray", boxwex=.2)
s <- b$stats
text(1:ncol(s)+.4, s[3,], round(s[3,],1), col="red")
