Learn R

Basic console commands in R

The R environment can be used to compute calculations and assign variables. As a new R-user, you might want to practice these simple exercises by typing them into the console window:

Data Types in R

There are different data types in R. These data types can be numeric, integer, logical/boolean, character/string, vector, matrix, array, list, data-frame. It is useful to know the data type in order to know what functions can be performed on the object.

To determine the type of data, you can use the class(), mode() or typeof() functions. The following commands create different variables and check their type using the class() function.

It is possible to convert from one data type to another by using functions such as as.integer(), as.vector(), as.matrix() etc.

Type typeof(df).  You will see the dataset we are using is type “data frame”.

Data Structures

Data Frame

• Each column is a variable, each row is an observation
• Internally, each column is a vector

df1<- data.frame(col1 = v1, col2 = v2, v3)

nrow(df1); dim(df1); ncol(df1);

names(df1)
names(df1) <- c(....)

rownames(df1); rownames(df1) <- c(....)

head(df1); tail(df1)

class(df1)

df1['col1']; df1[1]

df1[c('col1','col3')]; df1[c(1,3)]

df1[c(1,3), 2:3] #returns data from row 1&3, columns 2 to 3

Data Table

What is a data table?

• Extends & enhances the of functionality of data frames

Differences - (data.table vs data.table)

• By default, data.frame turns character data into factors, while data.table does not
• Printing to the console, data.table intelligently only prints first 5 rows
• KEY DIFFERENCE - data.tables are faster because they are indexed like a database

dt1<-data.table(df1)

dt1[,'col1', with = FALSE]

tables()

key(dt1)

setkey(dt1,col1)

dt1[c('col1Value1','colValue2'),]

dt1[J('1', c('2','3')),]

dt1[,list(col = mean(col1), col2Sum = sum(col2)), by=list(col3, col4)]