Scilab/C2/Iteration/English-timed
From Script | Spoken-Tutorial
| Time | Narration |
| 00:01 | Welcome to the spoken tutorial on iterative calculations using Scilab. |
| 00:07 | I am using Scilab version 5.2 in Mac operating system |
| 00:11 | but these calculations should work in other versions and also in Scilab that runs in Linux and Windows. |
| 00:17 | I will use the code available in the file 'iteration.sce'. |
| 00:22 | I have opened this file using Scilab editor which I plan to use only as an editor. |
| 00:29 | Let us create a vector using the colon operator. 'i' is equal to 1 colon 5, |
| 00:38 | creates a vector from 1 to 5, in increments of 1. |
| 00:42 | In this command, 'i' is equal to 1 colon 2 colon 5. |
| 00:51 | We see that the middle argument of 2 indicates the increment. |
| 00:56 | 1 is the first argument where the vector starts. 'i' cannot go beyond 5, |
| 01:01 | it can be equal to 5, however. |
| 01:04 | Note that if the ending argument changes to 6 the result remains the same. |
| 01:09 | It is not difficult to explain this behavior. |
| 01:13 | Can you think for a moment why this happens? |
| 01:15 | We will now demonstrate the use of the for statement to perform iterative calculations. |
| 01:22 | for i is equal to 1 colon 2 colon 7 disp i end of for loop. |
| 01:28 | I will cut this, paste in Scilab console, press Enter. |
| 01:34 | This code prints out 'i' as we go through the loop. |
| 01:37 | The display is due to the command disp - the passed argument is displayed. |
| 01:42 | Recall that the for loop is used for integer values. |
| 01:45 | In this case, four integer values, namely, 1, 3, 5 and 7 are displayed. |
| 01:50 | The number of times the iterations take place is known as priori in for loops. |
| 01:56 | In the rest of this tutorial, we will stick to the default increment of 1. |
| 02:01 | Let us begin with the loop that displays 'i' equal to 1 to 5. |
| 02:10 | We will modify this code by introducing the break statement. |
| 02:18 | Note that 'i' is displayed only up to 2. |
| 02:22 | The iteration is not carried out till the last value of i, namely 5. |
| 02:27 | When i is equal to 2, the if block is executed for the first time. |
| 02:30 | The break command, however, terminates the loop. |
| 02:34 | If we want to get out of a loop when some intermediate condition is satisfied, we can use the break statement. |
| 02:40 | Note that "i is equal to 2" statement uses the "equal to" sign twice. |
| 02:45 | This is the standard way to compare the equality in programming languages. |
| 02:50 | The result of this comparison statement is a Boolean: true or false. |
| 02:56 | We will introduce the continue statement here, paste, press Enter. |
| 03:06 | This results in 'i' getting displayed only for 4 and 5. |
| 03:10 | For 'i' less than or equal to 3, as given by the i less than or equal to 3 statement, nothing happens. |
| 03:18 | The continue statement makes the program skip the rest of the loop. |
| 03:22 | Unlike the break statement, however, it does not exit the loop. |
| 03:25 | The parameter 'i' is incremented and all the calculations of the loop are executed for the new i. |
| 03:32 | We take a small break and show how to get help for operators of the type 'less than or equal to' (<=). |
| 03:38 | Let us type 'less than or equal to with help'. |
| 03:46 | This opens the Scilab Help Browser. |
| 03:51 | We see that the help is available under the option less. |
| 03:56 | So now after closing this, we type help less. |
| 04:06 | We see the required help instructions here. I will close this. |
| 04:11 | The for statement in Scilab is more powerful than in programming languages. |
| 04:16 | For example, let us perform a loop over a vector: |
| 04:24 | This script displays all values of 'v'. |
| 04:28 | Until now we have been displaying only the variables. |
| 04:32 | We can indeed display the result of a calculation as well. |
| 04:35 | The following code displays the square of the numbers. |
| 04:44 | We have spent quite a bit of time explaining the for loop. |
| 04:48 | Let us now move on to the while loops. |
| 04:50 | The while statement allows us to perform a loop when a Boolean expression is true. |
| 04:55 | At the beginning of the loop, if the expression is true, |
| 04:58 | the statements in the body of the while loop are executed. |
| 05:02 | If the program is written well, the expression becomes false and the loop is ended. |
| 05:08 | Now let us see an example for the while loop: |
| 05:15 | The values of 'i', from 1 to 6 are displayed. |
| 05:19 | Break and continue statements inside the while loop work exactly as they did in the for loop as we demonstrate using break: |
| 05:33 | We can see that the moment 'i' becomes equal to 3, the program exits the loop, thanks to the break statement. |
| 05:39 | You can also try the example for continue statement in while loop. |
| 05:44 | This brings us to the end of this spoken tutorial on iterative calculations using Scilab. |
| 05:50 | Spoken Tutorials are part of the Talk to a Teacher project, supported by the National Mission on Education through ICT. |
| 05:57 | More information on the same is available at the following link [1]. |
| 06:00 | Thanks for joining. Good bye. |
