R/C2/Creating-Matrices-using-Data-Frames/English-timed
From Script | Spoken-Tutorial
| 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 as dot 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 row-wise 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 row-wise 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 (9,10,11,12) and (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. |
