R/C2/Conditional-Statements/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to this tutorial on Conditional Statements. |
| 00:05 | In this tutorial, we will learn about, |
| 00:08 | Conditional statements |
| 00:12 | if, else, and else if statements |
| 00:16 | To understand this tutorial, you should know, |
| 00:21 | Basic data structures |
| 00:23 | Indexing and slicing data frames |
| 00:27 | If not, please locate the relevant tutorials on R on this website. |
| 00:35 | This tutorial is recorded on |
| 00:37 | Ubuntu Linux OS version 16.04 |
| 00:42 | R version 3.4.4 |
| 00:46 | RStudio version 1.1.463 |
| 00:51 | Install R version 3.2.0 or higher. |
| 00:57 | For this tutorial, we will use |
| 01:00 | A data frame moviesData.csv |
| 01:05 | A script file conditionalStats.R. |
| 01:10 | Please download these files from the Code files link of this tutorial. |
| 01:17 | I have downloaded and moved these files to conditionalStatements folder. |
| 01:23 | This folder is located in myProject folder on my Desktop. |
| 01:30 | I have also set conditionalStatements folder as my Working Directory. |
| 01:36 | Conditional statements are used to execute some logical conditions in the code. |
| 01:43 | if, else and else if are the basic conditional statements. |
| 01:49 | Let us switch to RStudio. |
| 01:53 | Open the script conditionalStats.R in RStudio. |
| 02:01 | Here, we have declared a vector inScore. |
| 02:05 | The elements of this vector represent the runs scored by India in three different one-day matches. |
| 02:14 | Similarly, we have declared another vector ausScore. |
| 02:20 | The elements of this vector represent the runs scored by Australia in three different one-day matches. |
| 02:29 | Run this script by clicking on the Source button. |
| 02:34 | movies data frame opens in the Source window. |
| 02:39 | This data frame will be used later in this tutorial. |
| 02:45 | Click on the script conditionalStats.R |
| 02:49 | Let us now find which country has won the first one day match. |
| 02:55 | In the Source window, type the following command. |
| 03:00 | It means that if the condition is TRUE then execute the expression inside the curly brackets. |
| 03:09 | Save the script and run the current line by pressing Ctrl+Enter keys simultaneously. |
| 03:19 | I will resize the Console window. |
| 03:23 | As India scored more runs than Australia in the first one day match, the message, India won the first ODI!, is displayed. |
| 03:35 | Let us now find which country won the second one day match. |
| 03:41 | I will resize the Console window. |
| 03:45 | In the Source window, type the following command. |
| 03:51 | Save the script and run the current line. |
| 03:55 | As Australia scored more runs than India in the second one day match, we should get a message, Australia won the second ODI!. |
| 04:07 | But no message is displayed on the Console. |
| 04:12 | Here the if statement will be executed only when India scores more runs than Australia in the second one day match. |
| 04:24 | Hence, we need to add an else statement with another expression. |
| 04:30 | This expression should be executed when the if condition is not satisfied. |
| 04:37 | Click on the last line of the if statement. |
| 04:43 | Now, type the following command. |
| 04:47 | Please note that the else statement begins on the same line where if statement ends. |
| 04:57 | Save the script and run the current line. |
| 05:01 | I will resize the Console window. |
| 05:06 | Now, we get a message, Australia won the second ODI! |
| 05:11 | There is another efficient way to write this if-else statement. |
| 05:19 | In the Source window, type the following command. |
| 05:24 | Here, we are using ifelse for comparing the elements of two different vectors. |
| 05:32 | Here the ifelse statement has three arguments. |
| 05:38 | test - It is an object which can be forced to a logical mode. |
| 05:43 | Here test is for the comparison of scores. |
| 05:49 | yes - It returns values for true elements of the test. |
| 05:54 | Here, the first statement represents the value of the true element. |
| 06:01 | no - It returns values for false elements of the test |
| 06:06 | The second statement represents the value of the false element. |
| 06:13 | Save the script and run the current line. |
| 06:17 | We get the same message, Australia won the second ODI! |
| 06:23 | In the Source window, scroll up to locate the two vectors. |
| 06:29 | In the third one day match, India and Australia have scored the same number of runs. |
| 06:36 | Let us use an ifelse logic to find out the winner in this case. |
| 06:43 | In the Source window, click on the next line after the ifelse statement. |
| 06:51 | Now type the following command. |
| 06:56 | Save the script and run the current line. |
| 07:00 | We get the message, Australia won the third ODI! This is not correct. |
| 07:08 | So, we need to modify our logic. |
| 07:11 | In the Source window, type the following command. |
| 07:16 | Please note that else if statement begins on the same line where if statement ends. |
| 07:25 | Run the current line. |
| 07:27 | I will resize the Console window. |
| 07:32 | Now, we got the correct message, Third ODI was a tie. |
| 07:37 | I will resize the Console window again. |
| 07:41 | A conditional structure contains only one if statement. |
| 07:47 | It may contain as many else if statements as you need |
| 07:53 | and only one else statement. |
| 07:57 | The else statement will be executed only when all the above if and else if statements are FALSE. |
| 08:07 | In the Source window, scroll up. |
| 08:11 | Here, we have used ifelse for comparing the elements of two different vectors. |
| 08:19 | Now, we will learn how to use ifelse statements for comparing the two columns of a data frame. |
| 08:28 | In the Source window, scroll down to locate the last ifelse statement. |
| 08:35 | In the Source window, click on movies data frame. |
| 08:40 | In the Source window, scroll from left to right. |
| 08:45 | This will enable us to see the remaining objects of movies data frame. |
| 08:51 | Let us compare the critics_score and audience_score. |
| 08:58 | We will add a new column named dev in the movies data frame, which will show 1, if audience_score is greater than critics_score and 0, otherwise. |
| 09:15 | Click on the script conditionalStats.R |
| 09:20 | In the Source window, type the following command. |
| 09:25 | Save the script and run the last two lines. |
| 09:31 | movies data frame opens in the Source window. |
| 09:36 | In the Source window, scroll from left to right. |
| 09:41 | A new column named dev has been added. It has 1 or 0. |
| 09:51 | Remember, 1 means audience_score is greater than critics_score. |
| 09:57 | Now, we will find the number of movies, in which audience_score is greater than critics_score. |
| 10:06 | For this, we will use the sum function along with the if condition. |
| 10:13 | Click on the script conditionalStats.R |
| 10:18 | In the Source window, type the following command. |
| 10:24 | Save the script and run the current line. |
| 10:28 | So, there are 312 movies, in which audience_score is greater than critics_score. |
| 10:37 | Let us summarize what we have learnt. |
| 10:41 | In this tutorial, we have learnt about, Conditional statements, if, else, and else if statements |
| 10:50 | We now suggest an assignment. |
| 10:53 | Use the built-in data set iris. |
| 10:57 | Find the species, in which Sepal.Length is greater than Petal.Length Count all such species. |
| 11:07 | The video at the following link summarises the Spoken Tutorial project. |
| 11:13 | Please download and watch it. |
| 11:16 | We conduct workshops using Spoken Tutorials and give certificates. |
| 11:22 | Please contact us. |
| 11:25 | Please post your timed queries in this forum. |
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| 11:34 | The FOSSEE team coordinates the TBC project. |
| 11:39 | For more details, please visit these sites. |
| 11:44 | The Spoken Tutorial project is funded by NMEICT, MHRD, Govt. of India |
| 11:50 | The script for this tutorial was contributed by Varshit Dubey (College of Engineering Pune). |
| 11:58 | This is Sudhakar Kumar from IIT Bombay signing off. |
| 12:03 | Thanks for watching. |
