4.4. Input to a script file

When a script file is executed, the variables that are used in the calculations within the file must have assigned values. The assignment of a value to a variable can be done in three ways:

1. The variable is defined in the script file.
2. The variable is defined in the command prompt.
3. The variable is entered when the script is executed.

This chunk introduces the concept that when you run a script file in MATLAB, any variables needed for calculations must have values assigned to them. There are three ways to do this. First, you can assign values directly within the script itself. Second, you can assign values using the command prompt, where commands can be entered interactively. Third, you can prompt the user to input values when the script runs, which is often done using the input command. This allows for more dynamic scripting where user input can change the behavior of the script.

Imagine you're cooking a recipe. When you start cooking (executing a script), you need to prepare certain ingredients (variables). You can either gather and measure these ingredients beforehand (define them in the script), ask someone to provide them while you're cooking (define them in the command prompt), or request the amount of each ingredient right as you are preparing each step (ask for input when the script runs). Each method has its advantages depending on the situation.

In this case, the variable is defined in the script file. When the file is executed, the user is prompted to assign a value to the variable in the command prompt. This is done by using the input command. Here is an example.

% This script file calculates the average of points
% scored in three games.
% The point from each game are assigned to a variable
% by using the input command.
game1 = input('Enter the points scored in the first game ');
game2 = input('Enter the points scored in the second game ');
game3 = input('Enter the points scored in the third game ');
average = (game1 + game2 + game3) / 3

Here, we focus on how to use the input command in a MATLAB script to get user-defined values. This is shown with an example script that asks the user to input scores from three games. The input command prompts the user in the command prompt to enter data, which is then stored in variables game1, game2, and game3. Finally, the script calculates the average score and stores it in the variable 'average'. This interaction makes the script flexible as different users can provide their respective scores each time the script is run.

Think of this like asking your friends for their scores in a game so you can calculate the average. Instead of calculating scores yourself, you ask each person to tell you their points. You take those called out scores, add them together, and then divide by the number of players to get the average. This is similar to what happens in the MATLAB script with input commands.

The following shows the command prompt when this script file (saved as example3) is executed.

>> example3
>> Enter the points scored in the first game 15
>> Enter the points scored in the second game 23
>> Enter the points scored in the third game 10
average =
16

This chunk presents a specific example of what happens when the script (named example3) is run. It shows the command prompt interactions where the user inputs scores for each game, and finally, the average score is calculated and displayed. This demonstrates how the script effectively captures user inputs through prompts and processes them to provide an output. Notice how it reflects continuous interaction, where each input affects the result.

Imagine a classroom setting where a teacher is gathering test scores from students. As each student responds with their score, the teacher records it. Once the teacher has all scores, she calculates the average and announces it to the class. Just like this interactive classroom scenario, the script takes input from the user in real-time and computes the average based on that input.

The input command can also be used to assign string to a variable. For more information, see MATLAB documentation.

Apart from numeric values, the input command in MATLAB can also be utilized to take string inputs. This means that users could be prompted to enter names, descriptions, or any other textual information that the script can utilize. While this chunk indicates that further details can be found in MATLAB’s documentation, it highlights the versatility of the input command in gathering various types of user data.

Consider a situation where you are filling out a form. Some sections require numerical data (like phone numbers) while others require text (like names). Just like that form, the input command in MATLAB allows users to input either type, making it flexible for different kinds of scripts.

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