Here, I briefly describe what each method used in the tutorial does. If you want extra information on the method, read the help page! (?method_name ).
read.csv() : returns a data frame with the data stored in a csv file.
mean() : returns the mean of a variable.
var() : returns the variance of a variable.
sd() : returns the standard deviation of a variable.
median() : returns the median of a variable.
summary() : returns a collection of summary statistics for a variable; mix, max, median, mean, 1st quartile and 3rd quartile.
tapply() : apply a method (e.g. mean() ) to a variable using a grouping factor (e.g. Genus)
levels() : returns the levels of a factor.
strsplit() : splits a string into pieces whenever a separator (e.g. “,”) occurs.
as.character() : cast an object to character. This the same as to say, treat this as if it was a character.
data.frame() : object to store data matrices.
cbind() : combine columns; you mostly used it to add columns to a dataset. The method rbind() works for rows.
sqrt() : returns the square root of a number.
length() : returns the length of a list.
names() : returns the names of the variables within an objects. You can use it to return the names of the columns in a data frame.
ls() : list the objects in my workspace.
rm() : remove an object in my workspace.
head() : return the first 10 lines of a data frame
na.omit : ignore rows with missing data (NA)
do.call : constructs and executes a function call from a name or a function and a list of arguments to be passed to it. (I took this directly from the help page!)