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Latest revision as of 15:42, 22 May 2020
Time  Narration 
00:01  Welcome to the spoken tutorial on Creating Matrices using Data Frames. 
00:08  In this tutorial, we will learn how to: 
00:12  Convert a data frame into a matrix 
00:16  Create a matrix in R 
00:19  Perform basic operations on matrices 
00:24  To understand this tutorial, you should know, 
00:28  Data frames and Vectors in R 
00:32  Basics of Matrices 
00:35  R script in RStudio 
00:39  How to set working directory in RStudio 
00:44  If not, please locate the relevant tutorials on R on this website. 
00:51  This tutorial is recorded on 
00:54  Ubuntu Linux OS version 16.04 
01:01  R version 3.4.4 
01:06  RStudio version 1.1.456 
01:12  Install R version 3.2.0 or higher. 
01:19  For this tutorial, we will use the data frame CaptaincyData.csv and a script file myMatrix.R. 
01:30  Please download these files from the Code files link of this tutorial. 
01:38  I have downloaded and moved these files to Matrices folder in myProject folder on the Desktop. 
01:48  I have also set Matrices folder as my Working Directory. 
01:55  Let us switch to RStudio. 
01:58  Open the script myMatrix.R in RStudio. 
02:04  For this, click on the script myMatrix.R 
02:10  Script myMatrix.R opens in RStudio. 
02:16  Here, I have used rm function to remove all existing variables from memory. 
02:25  This prevents errors such as use of older data. 
02:31  Run this script by clicking on the Source button. 
02:36  The captaincy data frame is displayed in the Source window. 
02:42  We need our data in a matrix form to: 
02:45  Calculate the inverse of a matrix 
02:50  Perform matrix operations like addition, subtraction, multiplication, etc. 
02:58  Hence, we need to learn how to convert a data frame into a matrix. 
03:05  Let us get back to RStudio. 
03:09  We will convert the values in first three rows of played, won and lost columns into a matrix. 
03:19  We will create a subset for extracting these values. 
03:24  Click on the script myMatrix.R 
03:28  In the Source window, type the following command Press Enter. 
03:35  I am resizing the Source window. 
03:39  Press Enter to go to the next line. 
03:43  Press Enter at the end of every command. 
03:48  1 colon 3 indicates that the first three rows are to be extracted. 
03:55  c is the concatenate vector command with names of each column within double quotes. 
04:03  Save the script and execute the current line. 
04:08  The variable subData appears in the Environment window. 
04:14  Click on the arrow before subData to expand its contents. 
04:20  Now, we will convert this subset into a matrix. 
04:25  In the Source window, type matrixA then press Alt and hyphen()keys simultaneously. 
04:34  Now type asdot matrix, within parentheses type subdata and press Enter. 
04:46  as.matrix function is used to convert the subdata into a matrix. 
04:53  In Source window, type print, within parentheses matrixA. 
05:00  Save the script and run these two lines. 
05:06  The content of matrixA is shown on the Console window. 
05:11  Now let us create a 3 by 3 identity matrix. 
05:17  Create a vector named values containing the rowwise values of a 3 by 3 identity matrix. 
05:26  In the Source window, type the following command and press Enter. 
05:33  Now we will create a variable matrixB to store the matrix created using vector values. 
05:42  In the Source window, type the following command. Press Enter. 
05:49  Press Enter to go to the next line. 
05:52  Here, I have used matrix function with following arguments: 
05:58  data of values vector 
06:01  number of rows as nrow equal to 3 
06:06  number of columns as ncol equal to 3 
06:11  byrow equal to TRUE indicates that, data provided has to be arranged rowwise in the matrix. 
06:20  Now, type print within parentheses type matrixB to show the contents of the matrix. 
06:27  Save the script and run the last three lines of code. 
06:34  The identity matrix is shown on the Console window. 
06:39  Now let us perform some arithmetic operations on matrices. 
06:44  I will resize the Source window. 
06:48  We will add and subtract matrices A and B. 
06:53  In the Source window, type matrixA space plus sign space matrixB. 
07:02  Next, type matrixA space minus sign space matrixB 
07:10  Save the script and run these two lines. 
07:15  I will resize the Console window to see the output properly. 
07:21  The resulting matrices are shown on the Console window. 
07:26  Let us perform multiplication of individual elements of two matrices. 
07:32  In the Source window, type matrixA space asterisk sign space matrixB 
07:42  Save the script and run the current lines. 
07:47  The resulting matrix is shown on the Console window. 
07:52  Now, we will perform a true matrix multiplication with these matrices. 
07:59  1st row of matrixA is multiplied by 1st column of matrixB. 
08:06  Hence number of columns of matrixA should be equal to the number of rows of matrixB. 
08:15  In the Source window, type matrixA space percentage sign asterisk percentage sign space matrixB. 
08:25  Save the script and run the current line. 
08:31  The resulting matrix is shown on the Console window. 
08:36  Now let us calculate the transpose and determinant of matrixA. 
08:43  In the Source window, type t and matrixA in parentheses. 
08:50  Now, type det and matrixA in parentheses. 
08:57  Save the script and run these two lines. 
09:02  The corresponding output is shown on the Console window. 
09:07  Let us summarize what we have learnt. 
09:11  In this tutorial, we have learnt how to: 
09:15  Convert a data frame into a matrix 
09:19  Create a matrix in R 
09:22  Perform basic operations on matrices 
09:27  We now suggest an assignment. 
09:31  Consider 2 vectors c(9,10,11,12) and c(13,14,15,16). 
09:42  Create a 4 by 2 matrix from these two vectors. 
09:47  For solution, please refer to the Additional materials section on this website. 
09:55  The video at the following link summarises the Spoken Tutorial project. 
10:00  Please download and watch it. 
10:03  We conduct workshops using Spoken Tutorials and give certificates. 
10:09  Please contact us. 
10:12  Please post your timed queries in this forum. 
10:17  Please post your general queries in this forum. 
10:21  The FOSSEE team coordinates the TBC project. 
10:25  For more details, please visit these sites. 
10:29  The Spoken Tutorial project is funded by NMEICT, MHRD, Govt. of India 
10:36  The script for this tutorial was contributed by Shaik Sameer (FOSSEE Fellow 2018). 
10:45  This is Sudhakar Kumar from IIT Bombay signing off. Thanks for watching. 