Difference between revisions of "R/C2/Lists-and-its-Operations/English"

Opening slide

Learning Objectives

• Create a list in R
• Access the elements of a list
• Perform indexing on lists
• Combine two lists

Pre-requisites

spoken-tutorial.org

• Data frames in R
• Matrices and vectors in R

If not, please locate the relevant tutorials on R on this website.

System Specifications

• Ubuntu Linux OS version 16.04
• R version 3.4.4
• RStudio version 1.1.456

Install R version 3.2.0 or higher.

Download files

• A data frame CaptaincyData.csv and
• A script file myList.R.

Please download these files from the Code files link of this tutorial.

Highlight CaptaincyData.csv and myList.R in the folder Lists

This folder is located in myProject folder on my Desktop.

I have also set this folder as my Working Directory.

subData <- captaincy[1:3, c("played", "won", "lost")]

matrixA <- as.matrix(subData)

Press Enter.

Press Enter at the end of every command.

myVector <- c(1:5)

In the Source window, type the following command.

Save the script and run the last three lines of code by pressing Ctrl + Enter keys simultaneously.

List in R

It has components of mixed data types like

• strings
• numbers
• vectors
• some other list inside it.

A list can also contain a matrix or a function as its elements.

List in R

• A vector having all elements of the same type is called atomic vector, whereas
• A vector having elements of different type is called list

Highlight captaincy, matrixA and myVector in the Environment window

myList <- list(captaincy, matrixA, myVector)

For this, we will use names function.

names(myList) <- c("dataframe", "matrix", "vector")

Highlight matrix in the Source window

Highlight vector in the Source window

• dataframe to captaincy.
• matrix to matrixA
• vector to myVector

print(myList)

Highlight the output in the Console window

I am resizing the Console window.

In the Console window, three elements of myList are shown with their respective names.

Hence, myList is a named list.

In case of named lists, it can also be accessed by using the names.

myList$dataframe

Index of matrix is 2 in myList.

myList[2]

[RStudio]

myList2[,3]

In the Source window, type the following command.

Highlight 2 in the Source window

Highlight [,3] in the Source window

Remember we use single square bracket

notation with two indices for indexing a data frame.

First index and second index refer to row and column respectively.

Also, leaving an index blank indicates that we

want to keep all the elements in that dimension.

listSimple <- list("One", "Two", "Three")

In the Source window, type the following command.

Save the script and run the current line.

merged.list <- c(myList, listSimple)

print(merged.list)

It is used for storing the combined output of myList and listSimple.

In the Source window, type the following commands.

Highlight the output in the Console window

I am maximizing the Console window.

Now, scroll up to locate the output.

The combined list is shown on the Console.

Summary

• Create a list in R
• Access the elements of a list
• Perform indexing on lists
• Combine two lists

Assignment

• Create a numeric vector c(1:5) and a 5 by 3 matrix with elements from 1 to 15.
• Create a named list with vector, matrix and iris data set.
• Retrieve the iris data set from the list using dollar operator and indexing method.
• State the differences between the results obtained by using dollar operator and indexing method of accessing iris.

For solutions, please refer to the Additional Material section on this website.

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Acknowledgement

Thank You

This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching.