A switch statement is an alternative to if-elseif-else for the specific case of comparing one value against several possible exact matches. Anything a switch statement can do could also be written with if-elseif, but when you’re checking a single variable against a list of specific values, switch is often easier to read.

The MATLAB Help Center has documentation on switch.

Syntax

switch expression
    case value1
        statements1
    case value2
        statements2
    otherwise
        statements3
end

MATLAB evaluates expression once, then compares the result against each case value in order. The statements under the first matching case run, and then MATLAB jumps straight to after the end keyword - unlike some other languages, MATLAB does not fall through to the next case. If nothing matches, the otherwise block runs; like else, it’s optional.

For example:

status_code = 2;

switch status_code
    case 1
        disp('Nominal')
    case 2
        disp('Warning')
    case 3
        disp('Critical')
    otherwise
        disp('Unknown status code')
end


Warning

Matching Multiple Values in One Case

A single case can match more than one value by listing them in curly braces, {}. This is a place where switch is noticeably more compact than the equivalent if-elseif.

Example: Propulsion Type Lookup

Question

A database stores each rocket engine’s propulsion type as a numeric code: 1 for solid, 2 or 3 for the two liquid-engine variants in use, and 4 for electric. Write a MATLAB script that converts an engine’s code into a readable propulsion type.

Solution

Because codes 2 and 3 should both map to 'Liquid', we can group them into a single case instead of writing two separate cases with identical statements:

engine_code = 3;

switch engine_code
    case 1
        engine_type = 'Solid';
    case {2, 3}
        engine_type = 'Liquid';
    case 4
        engine_type = 'Electric';
    otherwise
        engine_type = 'Unknown';
end

disp(engine_type)


Liquid

Strings and Switch

switch also works on strings, comparing expression against each case value with the same rules as strcmp. This comes up often when a variable represents a named mode or state rather than a number, for example:

switch flight_phase
    case 'ascent'
        disp('Throttle for max Q')
    case 'coast'
        disp('Engines off')
    case 'descent'
        disp('Prepare for landing')
end

Reading Questions

  1. When is a switch statement a better choice than if-elseif?
  2. Does MATLAB’s switch statement fall through to the next case after a match, like some other languages?
  3. How would you write a single case that matches either the value 5 or the value 10?
  4. What does the otherwise block do, and is it required?
  5. Can a switch statement compare strings as well as numbers?