R/C2/Operations-on-Matrices-and-Data-Frames/English - Revision history

Sudhakarst at 12:16, 19 March 2019

2019-03-19T12:16:03Z

Nancyvarkey at 15:56, 18 March 2019

2019-03-18T15:56:08Z

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Sudhakarst at 11:16, 14 March 2019

2019-03-14T11:16:20Z

Sudhakarst at 18:02, 13 March 2019

2019-03-13T18:02:05Z

Sudhakarst at 18:00, 13 March 2019

2019-03-13T18:00:46Z

Sudhakarst: Created page with "'''Title of script''': Operations on Matrices and Data Frames '''Author''': Shaik Sameer (IIIT Vadodara) and Sudhakar Kumar (IIT Bombay) '''Keywords''': R, RStudio, matrices..."

2019-03-13T17:59:13Z

Created page with "'''Title of script''': Operations on Matrices and Data Frames '''Author''': Shaik Sameer (IIIT Vadodara) and Sudhakar Kumar (IIT Bombay) '''Keywords''': R, RStudio, matrices..."

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'''Title of script''': Operations on Matrices and Data Frames

'''Author''': Shaik Sameer (IIIT Vadodara) and Sudhakar Kumar (IIT Bombay)

'''Keywords''': R, RStudio, matrices, data frames, adding row, adding column, video tutorial

{| border =1
|'''Visual Cue’’’
|'''Narration’’’
|-
|| Show slide

Opening slide
|| Welcome to the spoken tutorial on '''Operations on Matrices and Data Frames'''.
|-
|| Show slide

Learning Objectives
|| In this tutorial, we will learn how to:
* Perform operations on matrices
* Add rows or columns to a '''data frame'''

|-
|| Show slide

Pre-requisites
|| To understand this tutorial, you should know
* '''Data frames''' and '''Matrices''' in '''R'''
* '''R script '''in''' RStudio'''
* How to set working directory in '''RStudio'''

If not, please locate the relevant tutorials on '''R''' on this website.
|-
|| Show slide

System Specifications

|| This tutorial is recorded on
* '''Ubuntu Linux''' OS version '''16.04'''
* '''R''' version '''3.4.4'''
* '''RStudio''' version '''1.1.456'''

Install''' R''' version '''3.2.0''' or higher.
|-
|| Show slide

Download Files
|| For this tutorial, we will use the '''data frame CaptaincyData.csv '''and the '''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 '''MatrixOps'''
|| I have downloaded and moved these files to '''MatrixOps '''folder''' '''in '''myProject''' folder on the '''Desktop'''.

I have also set '''MatrixOps''' 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 '''matrixA''' in the '''Source''' widow
|| Recall that, we had created a matrix named '''matrixA.'''

This matrix was extracted as a subset from the '''captaincy''' '''data frame'''.

We will use '''matrixA''' here also.
|-
|| Highlight the '''Source''' button
|| Run this '''script''' '''myMatrix.R''' to load the values in the '''Workspace'''.
|-
|| Highlight '''captaincy''' in the '''Source''' window
|| '''captaincy data frame''' opens in the '''Source''' window.
|-
||
|| I will resize the '''Source''' window.
|-
|| Highlight '''matrixA''' in the '''Environment '''window''' '''
|| Now let us learn how to find the inverse of '''matrixA'''.
|-
||
|| Click on the''' script myMatrix.R'''
|-
|| [RStudio]

'''solve(matrixA)'''
|| In the '''Source''' window, type '''solve, '''within parentheses''' matrixA'''.

Press '''Enter'''.

Press '''Enter''' at the end of every command.
|-
|| Press '''Ctrl + S''' >> Press '''Ctrl+Enter''' keys.
|| Save the '''script''' and run this line.
|-
|| Highlight the output in the Console window
|| The inverse of '''matrixA''' in shown in the '''Console '''window.
|-
||
|| For more information on calculating inverse of a '''matrix''' in '''R''', please refer to the '''Additional materials''' section on this website.
|-
|| [RStudio]

Highlight '''matrixA''' in the '''Environment''' window
|| Now let us calculate the sum of all the elements in '''matrixA'''.

First, we shall use '''nested for''' loops for calculating this sum.

Also, we shall estimate the time taken to calculate the sum in this way.
|-
|| [RStudio]

'''#''' '''Calculating sum using for loop '''
|| let us add a comment '''Calculating sum using for loop '''in the '''script'''.

In the '''Source''' window, type '''# hash''' space '''Calculating sum using for loop'''. Press '''Enter'''.
|-
|| [RStudio]

'''startTime <- Sys.time()'''
|| To calculate the time taken, we record the present time.

In the '''Source''' window, type '''startTime''' then press '''Alt '''and '''-'''('''hyphen''')''' '''keys simultaneously.

Next, type''' Sys''' dot '''time''' followed by parentheses.
|-
|| Highlight '''Sys.time''' in the '''Source''' window
|| '''Sys.time()''' is used to find the absolute date-time value in the current time zone.
|-
|| [RStudio]

'''totalSum <- 0'''
|| Let us initialise a variable '''totalSum'''.

In the '''Source''' window, type '''totalSum''' then press '''Alt '''and''' -'''('''hyphen''')''' '''keys simultaneously.

Then type 0.

This variable will store the sum of elements in '''matrixA'''.
|-
|| [RStudio]

'''for(i in 1:3) {'''

'''}'''
|| We will create two '''for''' loops to iterate through the rows and columns of the '''matrixA'''.

In the '''Source''' window, type '''for '''in parentheses''' i''' space '''in''' space 1 '''colon '''3 space

Now type opening curly bracket. '''RStudio''' automatically adds a closing curly bracket.
|-
|| [RStudio]

'''for(j in 1:3) {'''

'''totalSum <- totalSum + matrixA[i,j]'''

'''}'''
|| Press '''Enter''' just after the opening curly bracket and type the following command.
|-
|| [RStudio]

'''print(totalSum)'''
|| Press Enter after the closing curly bracket of outer loop '''for(i in 1:3)'''.

In the '''Source''' window, type '''print totalSum''' in''' parentheses'''.
|-
|| [RStudio]

'''endTime <- Sys.time()'''

'''endTime - startTime'''
|| Now, we record the current time again.

Type '''endTime '''then press '''Alt '''and '''-'''('''hyphen''')''' '''keys simultaneously.

Now type '''Sys''' dot '''time''' parentheses. Press '''Enter'''.

Type '''endTime '''space minus sign space''' startTime''' to know the total time taken and save the '''script'''.

I am resizing the '''Source '''window.
|-
|| [RStudio]

Highlight the sum in '''Console''' window
|| Run the block of code from the comment line '''Calculating sum using for loop '''to the end.

The '''totalSum''' is evaluated to be 237.
|-
|| [RStudio]

Highlight the time taken in '''Console''' window
|| The time taken to calculate the sum of elements in '''matrixA''' using '''for''' loop is approximately 8 milliseconds.

However, it may vary from system to system.
|-
|| Highlight '''matrixA''' in the '''Source''' window
|| Now, let us calculate the sum of all elements in '''matrixA''' using the '''sum''' function.
|-
||
|| We shall estimate the time taken to calculate the sum in this way also.
|-
|| [RStudio]

'''#''' '''Calculating sum using inbuilt function'''
|| In the script '''myMatrix.R''', add a comment '''Calculating sum using inbuilt function'''.

In the '''Source''' window, type '''# hash''' space '''Calculating sum using inbuilt function'''.
|-
|| [RStudio]

'''startTime <- Sys.time() '''

'''sum(matrixA)'''

'''endTime <- Sys.time()'''

'''endTime - startTime '''
|| Now, type the following commands.
|-
|| [RStudio]

Highlight the time taken in the '''Console''' window
|| Save the script and run the block of code from the comment line '''Calculating sum using inbuilt function '''to the end.

The time taken to calculate the sum of elements using '''sum''' function is 1.6 milliseconds.

Whereas, it took 8 milliseconds to calculate the same sum using '''for''' loop.
|-
|| Cursor on the interface.
|| So, it is advisable to use inbuilt functions of '''R'''.
|-
|| Cursor on the interface
|| Let us learn how to calculate sum of each '''row''' and sum of each '''column'''.
|-
|| [RStudio]

'''rowSums(matrixA) '''

'''colSums(matrixA) '''
|| In the '''Source''' window, type '''rowSums matrixA '''in parentheses.''' '''

Next, type''' colSums matrixA '''in parentheses.''' '''

Save the '''script''' and run these two lines to see the corresponding sums on the '''Console'''.
|-
||
|| I am resizing the '''Console '''window to see the output properly.
|-
||
|| Now let us learn how to add rows and columns to an existing '''data frame'''.
|-
||
|| Click on the '''captaincy data frame'''.
|-
|| Highlight '''captaincy data frame''' in the '''Source''' window
|| Let us add a new row to the '''captaincy data frame.'''
|-
||
|| Click on the''' script myMatrix.R'''
|-
|| [RStudio]

'''captaincy <- rbind(captaincy, data.frame(names="Kohli", Y = 2016, played = 30, won = 20, lost = 9, victory = 20/30))'''
|| In the '''Source''' window, type the following command. Press '''Enter '''after the comma for better visibility. .
|-
||
|| I am resizing the '''Source '''window
|-
|| Highlight '''captaincy '''in the Source window
|| We have used '''rbind()''' function with the following arguments* name of the '''data frame''' to which we want to add the new row. Here, it is '''captaincy'''.
* the row to be added as an argument to '''data.frame()'''.

|-
|| Highlight '''data.frame''' in the '''Source '''window
|| To '''data.frame()''' function, we provide the values according to the columns of the actual data frame.* '''names''' = “Kohli”
* '''Y''' = 2016
* '''played''' = 30
* '''won''' = 20
* '''lost''' = 9
* '''victory''' = 20/30

|-
|| [RStudio]

'''View(captaincy)'''

Highlight new row in the '''Source''' window
|| In the '''Source''' window, type '''View '''within''' parentheses captaincy'''

Save the '''script''' and run the last two lines of code.

One new row with the details of '''Kohli''' is added in the '''captaincy data frame'''.
|-
|| [RStudio]

'''defeat <- captaincy$lost / captaincy$played'''
|| Now let us create a new column named '''defeat''' from the '''captaincy data frame'''.

Click on the '''script myMatrix.R'''.

In the '''Source''' window, type''' '''the following command Press '''Enter'''.
|-
|| '''captaincy <- cbind(captaincy, defeat)'''

|| Now we add '''defeat''' as a new column in '''captaincy data frame'''.

In the '''Source''' window, type''' '''the following command Press '''Enter'''.
|-
|| Highlight '''cbind '''in the '''Source '''window
|| We have used '''cbind()''' function with following two arguments:* name of the '''data frame''' to which we want to add the new column. Here, it is '''captaincy'''.
* name of the column to be added. Here, it is '''defeat'''.

|-
|| '''View(captaincy)'''
|| Now type '''View, captaincy '''in''' parentheses '''

Save the '''script''' and run the block of code starting from the declaration of '''defeat '''to the end.

One column of '''defeat''' is added in the '''captaincy data frame'''.
|-
||
|| Let us summarize what we have learnt.
|-
|| Show slide

Summary

|| In this tutorial, we have learned how to:
* Perform operation on '''matrices'''
* Add rows or columns to a '''data frame'''

|-
|| Show slide

Assignment

|| We now suggest an assignment.
* Consider 2 vectors c(9,10,11,12) and c(13,14,15,16).
* Create a 4 by 2 matrix from these two vectors.
* Add another vector c(17,18,19,20) as a column to the previous matrix.

For solutions, 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.
|-
|}

@@ Line 137: / Line 137: @@
 |-
 || Highlight '''Sys.time''' in the '''Source''' window
-|| '''Sys.time()''' is used to find the absolute date-time value in the current time zone.
+|| '''Sys.time()''' is used to find the absolute date-time value in the current time.
 |-
 || [RStudio]
@@ Line 315: / Line 315: @@
 '''defeat <- captaincy$lost / captaincy$played'''
-|| Now let us create a new column named '''defeat''' from the '''captaincy data frame'''.
+|| Now let us create a new column named '''defeat''' in the '''captaincy data frame'''.
 Click on the '''script myMatrix.R'''.
@@ Line 340: / Line 340: @@
 Save the '''script''' and run the block of code starting from the declaration of '''defeat '''to the end.
-One column of '''defeat''' is added in the '''captaincy data frame'''.
+'''defeat''' column is added in the '''captaincy data frame'''.
 |-
 ||

@@ Line 4: / Line 4: @@
 '''Keywords''': R, RStudio, matrices, data frames, adding row, adding column, video tutorial
 {| border =1
@@ Line 131: / Line 130: @@
 || To calculate the time taken, we record the present time.
-In the '''Source''' window, type '''startTime''' then press '''Alt '''and '''-'''('''hyphen''')''' '''keys simultaneously.
+In the '''Source''' window, type '''start''' '''Time''' with capital T, then press '''Alt '''and '''-'''('''hyphen''')''' '''keys simultaneously.
 Next, type''' Sys''' dot '''time''' followed by parentheses.
@@ Line 154: / Line 153: @@
 '''}'''
-|| We will create two '''for''' loops to iterate through the rows and columns of the '''matrixA'''.
+|| Now, we will create two '''for''' loops to iterate through the rows and columns of the '''matrixA'''.
 In the '''Source''' window, type '''for '''in parentheses''' i''' space '''in''' space 1 '''colon '''3 space

@@ Line 279: / Line 279: @@
 |-
 || Highlight '''captaincy '''in the Source window
-|| We have used '''rbind()''' function with the following arguments* name of the '''data frame''' to which we want to add the new row. Here, it is '''captaincy'''.
+|| We have used '''rbind()''' function with the following arguments
 * the row to be added as an argument to '''data.frame()'''.
 |-
 || Highlight '''data.frame''' in the '''Source '''window
-|| To '''data.frame()''' function, we provide the values according to the columns of the actual data frame.* '''names''' = “Kohli”
+|| To '''data.frame()''' function, we provide the values according to the columns of the actual data frame.
 * '''Y''' = 2016
 * '''played''' = 30
@@ Line 319: / Line 321: @@
 |-
 || Highlight '''cbind '''in the '''Source '''window
-|| We have used '''cbind()''' function with following two arguments:* name of the '''data frame''' to which we want to add the new column. Here, it is '''captaincy'''.
+|| We have used '''cbind()''' function with following two arguments:
 * name of the column to be added. Here, it is '''defeat'''.

@@ Line 7: / Line 7: @@
 {| border =1
-|'''Visual Cue’’’
+|'''Visual Cue'''
-|'''Narration’’’
+|'''Narration'''
 |-
 || Show slide
@@ Line 21: / Line 21: @@
 * Perform operations on matrices
 * Add rows or columns to a '''data frame'''
 |-
@@ Line 49: / Line 48: @@
 Download Files
 || For this tutorial, we will use the '''data frame CaptaincyData.csv '''and the '''script '''file '''myMatrix.R'''.
 Please download these files from the '''Code files''' link of this tutorial.
@@ Line 57: / Line 55: @@
 Highlight '''CaptaincyData.csv '''and '''myMatrix.R''' in the folder '''MatrixOps'''
 || I have downloaded and moved these files to '''MatrixOps '''folder''' '''in '''myProject''' folder on the '''Desktop'''.
 I have also set '''MatrixOps''' folder as my '''Working directory'''.
@@ Line 65: / Line 62: @@
 |-
 || 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.'''
@@ Line 78: / Line 72: @@
 || Highlight '''matrixA''' in the '''Source''' widow
 || Recall that, we had created a matrix named '''matrixA.'''
 This matrix was extracted as a subset from the '''captaincy''' '''data frame'''.
 We will use '''matrixA''' here also.
@@ Line 104: / Line 96: @@
 '''solve(matrixA)'''
 || In the '''Source''' window, type '''solve, '''within parentheses''' matrixA'''.
 Press '''Enter'''.
 Press '''Enter''' at the end of every command.
@@ Line 165: / Line 155: @@
 '''}'''
 || We will create two '''for''' loops to iterate through the rows and columns of the '''matrixA'''.
 In the '''Source''' window, type '''for '''in parentheses''' i''' space '''in''' space 1 '''colon '''3 space
 Now type opening curly bracket. '''RStudio''' automatically adds a closing curly bracket.
@@ Line 207: / Line 195: @@
 Highlight the sum in '''Console''' window
 || Run the block of code from the comment line '''Calculating sum using for loop '''to the end.
 The '''totalSum''' is evaluated to be 237.
@@ Line 246: / Line 233: @@
 Highlight the time taken in the '''Console''' window
 || Save the script and run the block of code from the comment line '''Calculating sum using inbuilt function '''to the end.
 The time taken to calculate the sum of elements using '''sum''' function is 1.6 milliseconds.
 Whereas, it took 8 milliseconds to calculate the same sum using '''for''' loop.
@@ Line 296: / Line 281: @@
 || We have used '''rbind()''' function with the following arguments* name of the '''data frame''' to which we want to add the new row. Here, it is '''captaincy'''.
 * the row to be added as an argument to '''data.frame()'''.
 |-
@@ Line 306: / Line 290: @@
 * '''lost''' = 9
 * '''victory''' = 20/30
 |-
@@ Line 330: / Line 313: @@
 |-
 || '''captaincy <- cbind(captaincy, defeat)'''
 || Now we add '''defeat''' as a new column in '''captaincy data frame'''.
@@ Line 340: / Line 321: @@
 || We have used '''cbind()''' function with following two arguments:* name of the '''data frame''' to which we want to add the new column. Here, it is '''captaincy'''.
 * name of the column to be added. Here, it is '''defeat'''.
 |-
@@ Line 356: / Line 336: @@
 Summary
 || In this tutorial, we have learned how to:
 * Perform operation on '''matrices'''
 * Add rows or columns to a '''data frame'''
 |-
@@ Line 368: / Line 344: @@
 Assignment
 || We now suggest an assignment.