Difference between revisions of "R/C2/CreatingMatricesusingDataFrames/English"
Sudhakarst (Talk  contribs) 
Nancyvarkey (Talk  contribs) 

Line 72:  Line 72:  
    
 Highlight '''rm '''in '''Source '''window   Highlight '''rm '''in '''Source '''window  
−   Here, I have used '''rm '''  +   Here, I have used '''rm function''' to remove all existing variables from memory. 
This prevents errors such as use of older data.  This prevents errors such as use of older data.  
Line 88:  Line 88:  
 We need our data in a '''matrix''' form to:   We need our data in a '''matrix''' form to:  
* Calculate the inverse of a''' matrix'''  * Calculate the inverse of a''' matrix'''  
−  * Perform matrix operations like addition, subtraction, multiplication, etc.  +  * Perform '''matrix''' operations like addition, subtraction, multiplication, etc. 
Hence, we need to learn how to convert a''' data frame''' into a '''matrix'''.  Hence, we need to learn how to convert a''' data frame''' into a '''matrix'''.  
Line 124:  Line 124:  
 '''1 colon 3''' indicates that the first three rows are to be extracted.   '''1 colon 3''' indicates that the first three rows are to be extracted.  
−  '''c''' is the concatenate vector command with names of each column within double quotes.  +  '''c''' is the '''concatenate vector command''' with names of each column within double quotes. 
    
 Press '''Ctrl + S''' >> Press '''Ctrl+Enter''' keys.   Press '''Ctrl + S''' >> Press '''Ctrl+Enter''' keys.  
Line 149:  Line 149:  
    
 Highlight '''as.matrix''' in the '''Source '''window   Highlight '''as.matrix''' in the '''Source '''window  
−   '''as.matrix'''  +   '''as.matrix function''' is used to convert the '''subdata '''into a '''matrix'''. 
    
 [RStudio]   [RStudio]  
Line 188:  Line 188:  
Highlight '''byrow''' in the '''Source''' window  Highlight '''byrow''' in the '''Source''' window  
−   Here, I have used '''matrix'''  +   Here, I have used '''matrix function''' with following '''arguments''': 
* data of '''values''' vector  * data of '''values''' vector  
* number of rows as '''nrow '''equal to''' 3 '''  * number of rows as '''nrow '''equal to''' 3 '''  
* number of columns as '''ncol '''equal to''' 3'''  * number of columns as '''ncol '''equal to''' 3'''  
−  * '''byrow '''equal to''' TRUE''' indicates that, data provided has to be arranged rowwise in the matrix.  +  * '''byrow '''equal to''' TRUE''' indicates that, data provided has to be arranged rowwise in the '''matrix'''. 
    
Line 201:  Line 201:  
    
 Press''' Ctrl + S''' keys >> Highlight three lines >> Press '''Ctrl + Enter''' keys   Press''' Ctrl + S''' keys >> Highlight three lines >> Press '''Ctrl + Enter''' keys  
−   Save the '''script''' and run the last three lines  +   Save the '''script''' and run the last three lines of code. 
    
 Highlight the output in the '''Console''' window   Highlight the output in the '''Console''' window  
−   The '''identity  +   The '''identity matrix''' is shown on the '''Console''' window. 
    
 Cursor on the interface.   Cursor on the interface.  
Line 217:  Line 217:  
'''matrixA  matrixB '''  '''matrixA  matrixB '''  
−   We will add and subtract '''matrices  +   We will add and subtract '''matrices A''' and '''B'''. 
−  In the '''Source''' window, type '''matrixA '''space''' plus '''sign  +  In the '''Source''' window, type '''matrixA '''space''' plus '''sign space''' matrixB ''' 
−  Next, type '''matrixA '''space''' minus '''sign  +  Next, type '''matrixA '''space''' minus '''sign space''' matrixB ''' 
    
 Press '''Ctrl + S''' >> Press '''Ctrl+Enter''' keys.   Press '''Ctrl + S''' >> Press '''Ctrl+Enter''' keys.  
Line 230:  Line 230:  
I will resize the '''Console''' window to see the output properly.  I will resize the '''Console''' window to see the output properly.  
−  The resulting matrices are shown on the '''Console''' window.  +  The resulting '''matrices''' are shown on the '''Console''' window. 
    
 [RStudio]   [RStudio]  
'''matrixA * matrixB '''  '''matrixA * matrixB '''  
−   Let us perform multiplication of individual elements of two '''matrices'''.  +   Let us perform multiplication of individual '''elements''' of two '''matrices'''. 
In the Source window, type '''matrixA '''space''' asterisk '''sign''' '''space''' matrixB '''  In the Source window, type '''matrixA '''space''' asterisk '''sign''' '''space''' matrixB '''  
Line 244:  Line 244:  
 Save the '''script''' and run the current lines.   Save the '''script''' and run the current lines.  
−  The resulting matrix is shown on the '''Console''' window.  +  The resulting '''matrix''' is shown on the '''Console''' window. 
    
 Highlight '''matrixA''' and '''matrixB''' in '''Environment''' window   Highlight '''matrixA''' and '''matrixB''' in '''Environment''' window  
Line 261:  Line 261:  
 Save the '''script''' and run the current line.   Save the '''script''' and run the current line.  
−  The resulting matrix is shown on the '''Console''' window.  +  The resulting '''matrix''' is shown on the '''Console''' window. 
    
 Cursor on the interface.   Cursor on the interface.  
Line 297:  Line 297:  
 We now suggest an assignment.   We now suggest an assignment.  
−  * Consider 2 vectors c(9,10,11,12) and c(13,14,15,16).  +  * Consider 2 '''vectors''' c(9,10,11,12) and c(13,14,15,16). 
−  * Create a 4 by 2 matrix from these two vectors.  +  * Create a 4 by 2 '''matrix''' from these two '''vectors'''. 
+  
For solution, please refer to the '''Additional materials''' section on this website.  For solution, please refer to the '''Additional materials''' section on this website.  
   
Revision as of 22:46, 4 March 2019
Title of script: Creating Matrices using Data Frames
Author: Shaik Sameer (IIIT Vadodara) and Sudhakar Kumar (IIT Bombay)
Keywords: R, RStudio, matrices, data frames, transpose, determinant, video tutorial.
Visual Cue  Narration 
Show slide
Opening slide 
Welcome to the spoken tutorial on Creating Matrices using Data Frames. 
Show slide
Learning Objectives 
In this tutorial, we will learn how to:

Show slide
Prerequisites spokentutorial.org 
To understand this tutorial, you should know
If not, please locate the relevant tutorials on R on this website. 
Show slide
System Specifications 
This tutorial is recorded on
Install R version 3.2.0 or higher. 
Show slide
Download Files 
For this tutorial, we will use the data frame CaptaincyData.csv and a script file myMatrix.R.
Please download these files from the Code files link of this tutorial. 
[Computer screen]
Highlight CaptaincyData.csv and myMatrix.R in the folder Matrices 
I have downloaded and moved these files to Matrices folder in myProject folder on the Desktop.
I have also set Matrices folder as my Working Directory. 
Let us switch to RStudio.  
Click myMatrix.R in RStudio
Point to myMatrix.R in Rstudio. 
Open the script myMatrix.R in RStudio.
For this, click on the script myMatrix.R Script myMatrix.R opens in RStudio. 
Highlight rm in Source window  Here, I have used rm function to remove all existing variables from memory.
This prevents errors such as use of older data. 
Highlight Source button
Highlight captaincy in the Source window 
Run this script by clicking on the Source button.
The captaincy data frame is displayed in the Source window. 
Show slide
Data in Matrix Format 
We need our data in a matrix form to:
Hence, we need to learn how to convert a data frame into a matrix. 
Let us get back to RStudio.  
[RStudio]
Highlight the three rows of captaincy 
We will convert the values in first three rows of played, won and lost columns into a matrix.
We will create a subset for extracting these values. 
Highlight myMatrix.R in the Source window  Click on the script myMatrix.R 
[RStudio]
subdata < captaincy[1:3, c("played", "won", "lost")] 
In the Source window, type the following command Press Enter.
I am resizing the Source window. Press Enter to go to the next line. Press Enter at the end of every command. 
[RStudio]
Highlight 1:3 in the Source window Highlight c in the Source window 
1 colon 3 indicates that the first three rows are to be extracted.
c is the concatenate vector command with names of each column within double quotes. 
Press Ctrl + S >> Press Ctrl+Enter keys.  Save the script and execute the current line. 
[RStudio]
Highlight subData in the Environment window. Click on the arrow before subData. 
The variable subData appears in the Environment window.
Click on the arrow before subData to expand its contents. 
Now, we will convert this subset into a matrix.  
[RStudio]
matrixA < as.matrix(subdata) 
In the Source window, type matrixA then press Alt and (hyphen) keys simultaneously.
Now type as dot matrix, within parentheses type subdata and press Enter. 
Highlight as.matrix in the Source window  as.matrix function is used to convert the subdata into a matrix. 
[RStudio]
print(matrixA) 
In Source window, type print, within parentheses matrixA. 
Press Ctrl + S >> Highlight two lines >> Press Ctrl+Enter keys.  Save the script and run these two lines. 
Highlight the output in the Console window  The content of matrixA is shown on the Console window. 
cursor on the interface.  Now let us create a 3 by 3 identity matrix.
Create a vector named values containing the row wise values of a 3 by 3 identity matrix. 
[RStudio]
values < c(1,0,0,0,1,0,0,0,1) 
In the Source window, type the following command and press Enter. 
[RStudio]
matrixB < matrix(values, nrow = 3, ncol = 3, byrow = TRUE) 
Now we will create a variable matrixB to store the matrix created using vector values.
In the Source window, type the following command. Press Enter. Press Enter to go to the next line. 
[RStudio]
Highlight values in the Source window Highlight nrow and ncol in the Source window Highlight byrow in the Source window 
Here, I have used matrix function with following arguments:

[RStudio]
print(matrixB) 
Now, type print within parentheses type matrixB to show the contents of the matrix. 
Press Ctrl + S keys >> Highlight three lines >> Press Ctrl + Enter keys  Save the script and run the last three lines of code. 
Highlight the output in the Console window  The identity matrix is shown on the Console window. 
Cursor on the interface.  Now let us perform some arithmetic operations on matrices. 
Highlight the boundary of Source window  I will resize the Source window. 
[RStudio]
matrixA + matrixB matrixA  matrixB 
We will add and subtract matrices A and B.
In the Source window, type matrixA space plus sign space matrixB Next, type matrixA space minus sign space matrixB 
Press Ctrl + S >> Press Ctrl+Enter keys.
Highlight the output on the Console window 
Save the script and run these two lines.
I will resize the Console window to see the output properly. The resulting matrices are shown on the Console window. 
[RStudio]
matrixA * matrixB 
Let us perform multiplication of individual elements of two matrices.
In the Source window, type matrixA space asterisk sign space matrixB 
Press Ctrl + S >> Press Ctrl+Enter keys.
Highlight the output on the Console window 
Save the script and run the current lines.
The resulting matrix is shown on the Console window. 
Highlight matrixA and matrixB in Environment window  Now, we will perform a true matrix multiplication with these matrices.
1st row of matrixA is multiplied by 1st column of matrixB. Hence number of columns of matrixA should be equal to the number of rows of matrixB. 
matrixA %*% matrixB  In the Source window, type matrixA space percentage sign asterisk percentage sign space matrixB. 
Press Ctrl + S >> Press Ctrl+Enter keys.
Highlight the output on the Console window. 
Save the script and run the current line.
The resulting matrix is shown on the Console window. 
Cursor on the interface.  Now let us calculate the transpose and determinant of matrixA. 
[RStudio]t(matrixA)
det(matrixA) 
In the Source window, type t and matrixA in parentheses.
Now, type det and matrixA in parentheses. 
Press Ctrl + S >> Press Ctrl+Enter keys.
Highlight the output on the Console window. 
Save the script and run these two lines.
The corresponding output is shown on the Console window. 
Let us summarize what we have learnt.  
Show slide
Summary 
In this tutorial, we have learnt how to:

Show slide
Assignment 
We now suggest an assignment.
For solution, please refer to the Additional materials section on this website. 
Show slide
About the Spoken Tutorial Project 
The video at the following link summarises the Spoken Tutorial project.
Please download and watch it. 
Show slide
Spoken Tutorial Workshops 
We conduct workshops using Spoken Tutorials and give certificates.
Please contact us. 
Show Slide
Forum to answer questions 
Please post your timed queries in this forum. 
Show Slide
Forum to answer questions 
Please post your general queries in this forum. 
Show Slide
Textbook Companion 
The FOSSEE team coordinates the TBC project.
For more details, please visit these sites. 
Show Slide
Acknowledgement 
The Spoken Tutorial project is funded by NMEICT, MHRD, Govt. of India 
Show Slide
Thank You 
The script for this tutorial was contributed by Shaik Sameer (FOSSEE Fellow 2018).
This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching. 