MATLAB Control Statements
Objective: To study control structures (for, while, if, switch, break, continue, input/output functions, reading, and storing data).
If: If evaluates a logical expression and executes a group of statements based on the value of the expression.
Syntax of If Statement
if expression 1 statement1 elseif expression 2 statement 2 else statement 3 end
Examples
Output:
a is positive
Switch, case, and otherwise: Switch executes certain statements based on the value of a variable or expression. Its basic form is
Syntax
switch switch expression case case expression statements case case expression statements . . . otherwise statements end
An evaluated switch expression is a scaler or string. An evaluated case expression a scaler, a string, or a cell array of scaler or strings. The switch block tests each case is until one of the cases is true.
Examples
Conditionally display different text depending on value entered at the command line.
Output:
negative one
Example 2:
Output:
result is 52
Example 3:
Output:
weekend
For: A for loop is a repetition control operation that allows us to accurately write a loop that wants to perform a particular number of times.
Syntax
Examples
Output:
n = 1 a = 1 n = 2 a = 1 4 n = 3 a = 1 4 9 n = 4 a = 1 4 9 16 n = 5 a = 1 4 9 16 25 n = 6 a = 1 4 9 16 25 36 n = 7 a = 1 4 9 16 25 36 49 n = 8 a = 1 4 9 16 25 36 49 64 n = 9 a = 1 4 9 16 25 36 49 64 81 n = 10 a = 1 4 9 16 25 36 49 64 81 100
Example2:
Output:
1 0.9000 0.8000 0.7000 0.6000 0.5000 0.4000 0.3000 0.2000 0.1000 0
Example 3:
Output:
1 5 8 17
while: The while loop repeatedly executes statements while a specified statement is true.
Syntax
Examples:
Output:
2 6 42
break: The break statement terminates execution of for or while loops. Statements in the loop that appear after the break statement are not executed.
Examples
Output:
110
continue: The continue statement is used for passing control to the next iteration of a for or while loop.
Example
Output:
a = 1 a = 1 4 a = 1 4 9 a = 1 4 9 16 a = 1 4 9 16 25
pause: pause pauses the program for a set amount of time. If (…) is blank, then the program will pause until a key is pressed on the keyboard.
Load command: It loads data from a disk file into the current MATLAB workspace.
      load filename;
where filename is the name of the file to be load. If the file is a MAT-file, then all of the variables in the file will be restored with the name and types of the same as before.
E.g.: load -mat x.dat
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Save: save command saves data from the current MATLAB workspace into a disk file.
      save filename var1 var2 var3…
where filename is the name of the file where var1, var2, var3, etc. are saved. By default, the file name will be. mat. If no variable is specified, then the entire contents of the workspace will be saved.
If information must be exchanged between MATLAB and other programs, store the MATLAB data in ASCII format. If the data are used only in MATLAB, save the data in the mat file format.
Example:
X= [1.23 4.56 7.89 2.3] Save -ascii x.dat x;