Programming and Data Types

switch

switch executes certain statements based on the value of a variable or expression. Its basic form is

• switch expression (scalar or string)
      case value1
          statements % Executes if expression is value1
      case value2 
          statements % Executes if expression is value2
      .
      .
      .
      otherwise
          statements % Executes if expression does not
                        % does not match any case
  end
  

This block consists of:

• The word switch followed by an expression to evaluate.
• Any number of case groups. These groups consist of the word case followed by a possible value for the expression, all on a single line. Subsequent lines contain the statements to execute for the given value of the expression. These can be any valid MATLAB statement including another switch block. Execution of a case group ends when MATLAB encounters the next case statement or the otherwise statement. Only the first matching case is executed.
• An optional otherwise group. This consists of the word otherwise, followed by the statements to execute if the expression's value is not handled by any of the preceding case groups. Execution of the otherwise group ends at the end statement.
• An end statement.

switch works by comparing the input expression to each case value. For numeric expressions, a case statement is true if (value==expression). For string expressions, a case statement is true if strcmp(value,expression).

The code below shows a simple example of the switch statement. It checks the variable input_num for certain values. If input_num is -1, 0, or 1, the case statements display the value on screen as text. If input_num is none of these values, execution drops to the otherwise statement and the code displays the text 'other value'.

• switch input_num
      case -1
          disp('negative one');
      case 0
          disp('zero');
      case 1
          disp('positive one');
      otherwise
           disp('other value');
  end
  

Note    For C Programmers, unlike the C language switch construct, the MATLAB switch does not "fall through." That is, if the first case statement is true, other case statements do not execute. Therefore, break statements are not used.

switch can handle multiple conditions in a single case statement by enclosing the case expression in a cell array.

• switch var
      case 1
          disp('1')
      case {2,3,4}
          disp('2 or 3 or 4')
      case 5
          disp('5')
      otherwise
          disp('something else')
  end
  

if, else, and elseif

while