Difference between revisions of "Scilab/C2/Iteration/English-timed"
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Revision as of 16:08, 9 April 2013
| Time' | Narration
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| 00.02 | 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. |
| 00.18 | I will use the code available in the file iteration.sce |
| 00.23 | 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, |
| 00.52 | 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. |
| 01.10 | It is not difficult to explain this behaviour. |
| 01.13 | Can you think for a moment why this happens? |
| 01.16 | We will now demonstrate the use of the for statement to perform iterative calculations.
for i is equal to 1 colon 2 colon 7 disp i end of for loop. |
| 01.29 | I will cut this paste in scilab console press enter. |
| 01.35 | 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. |
| 01.53 | The number of times the iterations take place is known as priori in for loops. |
| 01.57 | 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. |
| 02.19 | 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. |
| 02.31 | 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. |
| 02.41 | Note that "i is equal to 2" statement uses the "equal to" sign twice. |
| 02.46 | This is the standard way to compare the equality in programming languages. |
| 02.51 | 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. |
| 03.11 | 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. |
| 03.33 | 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 |
| 03.47 | This opens the scilab help browser. |
| 03.52 | We see that the help is available under the option less. |
| 03.56 | So now after closing this we type help less |
| 04.07 | We see the required help instructions here. I will close this. |
| 04.12 | The for statement in Scilab is more powerful than in programming languages. |
| 04.16 | For example, let us perform a loop over a vector: |
| 04.25 | 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. |
| 04.45 | We have spent quite a bit of time explaining the for loop. |
| 04.48 | Let us now move on to the while loops. |
| 04.51 | The while statement allows us to perform a loop when a boolean expression is true |
| 04.56 | At the beginning of the loop, if the expression is true, |
| 04.59 | 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. |
| 05.40 | 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. |
| 05.51 | 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. |
