In this section, we will compare the code side by side to solve the same problem using both default R and plyr. Reusing the iris3 data, we are now interested in producing five-number summary statistics for each variable group by species. The five numbers will be minimum, mean, median, maximum, and standard deviation. The output will be a list of data frames.
To calculate the five-number summary statistics, follow these steps:
Define a function that will calculate five-number summary statistics for a given vector.
Produce the output of this function in a data frame object.
Apply this function in the
iris3dataset using aforloop.Apply the same function using the
apply()function of theplyrpackage.
An example that explains the calculation of the five-number summary statistics is as follows:
# Function to calculate five number summary
fivenum.summary <- function(x)
{
results <-data.frame(min=apply(x,2,min),
mean=apply(x,2,mean),
median=apply(x,2,median),
max...