Interquartile range

Add custom summary statistics in ggplot2

It is hard to understand your data by looking at the numbers on a csv file. You need to plot it. And adding statistics to your plots will make it more informative. To evaluate data, we typically use mean and median to define its central tendency and range, quartiles, variance and standard deviation to define how spread it is. Mean and standard deviation is a good representation of the data if we don’t have extreme values that result in a skewed distribution.