Writing scripts to solve problems  (Page 5/4)

MATLAB provides scripting and automation tools that can simplify repetitive computational tasks. For example, a series of commands executed in a MATLAB session to solve a problem can be saved in a script file called an m-file. An m-file can be executed from the command line by typing the name of the file or by pressing the run button in the built-in text editor tool bar.

Script files

A script is a file containing a sequence of MATLAB statements. Script files have a filename extension of .m. By typing the filename at the command prompt, we can run the script and obtain results in the command window.

A sample m-file named ThermalConductivity.m is displayed in Text Editor below. Note the triangle (in green) run button in the tool bar, pressing this button executes the script in the command window.

Now let us see how an m-file is created and executed.

A cylindrical acetylene bottle with a radius r=0.3 m has a hemispherical top. The height of the cylindrical part is h=1.5 m. Write a simple script to calculate the volume of the acetylene bottle.

To solve this problem, we will first apply the volume of cylinder equation . Using the volume of sphere equation , we will calculate the volume of hemisphere . The total volume of the acetylene bottle is found with the sum of volumes equation .

$$V_{\mathrm{cylinder}}=\pi r^{2}h$$

$$V_{\mathrm{sphere}}=\frac{4}{3}\pi r^3$$

$$V_{\mathrm{top}}=\frac{2}{3}\pi r^3$$

$$V_{\mathrm{acetylene\; bottle}}=V_{\mathrm{cylinder}}+V_{\mathrm{top}}$$

To write the script, we will use the built-in text editor. From the menu bar select File>New>Script. The text editor window will open in a separate window. First save this file as AcetyleneBottle.m . In that window type the following code paying attention to the use of percentage and semicolon symbols to comment out the lines and suppress the output, respectively.

% This script computes the volume of an acetylene bottle with a radius r=0.3 m, % a hemispherical top and a height of cylindrical part h=1.5 m.r=0.3; % Radius [m] h=1.5; % Height [m]Vol_top=(2*pi*r^3)/3; % Calculating the volume of hemispherical top [m3] Vol_cyl=pi*r^2*h; % Calculating the volume of cylindrical bottom [m3]Vol_total=Vol_top+Vol_cyl % Calculating the total volume of acetylene bottle [m3]

After running the script by pressing the green button in the Text Editor tool bar, the output is displayed in the command window as shown below.

The input Function

Notice that the script we have created above is not interactive and computes the total volume only for the variables defined in the m-file. To make this script interactive we will make some changes to the existing AcetyleneBottle.m by adding input function and save it as AcetyleneBottleInteractive.m .

The syntax for input is as follows: