Read data with

birth <- read.table("http://anaraven.github.io/static/birth.txt", header=TRUE)

plot(head ~ weight, data=birth)

birth$apgar5 <- as.factor(birth$apgar5)
plot(sex ~ apgar5, data=birth)

plot(sex ~ weight, data=birth)

plot(weight ~ sex, data=birth)

Plotting a numeric value depending on a factor results in a boxplot

It is a graphical version of summary().

• The center is the median
• The box is between the first and third quartile (50% of cases)
• The whiskers extend a prediction of 95% of cases
• Points are outliers

plot(weight ~ sex, data=birth, boxwex=0.2, notch=TRUE, col="grey")

plot(birth)