MATLAB Functions

Conditionally execute statements

if expression
    statements 
end
if expression1
    statements 
elseif expression2
    statements 
else
    statements 
end

Description

if

conditionally executes statements.

The simple form is:

if expression
    statements
end

More complicated forms use else or elseif. Each if must be paired with a matching end.

Arguments




expression
A MATLAB expression, usually consisting of smaller 
expressions or variables joined by relational operators (==, <, 
>, <=, >=, or ~=). Two examples are: count < limit and 
(height - offset) >= 0. 

Expressions may also include logical functions, as in: 
isreal(A).

Simple expressions can be combined by logical operators 
(&,|,~) into compound expressions such as: (count < limit) & 
((height - offset) >= 0).

statements
One or more MATLAB statements to be executed only if the 
expression is true (or nonzero). See Examples for information 
about how nonscalar variables are evaluated.

`expression`	A MATLAB expression, usually consisting of smaller expressions or variables joined by relational operators (`==`, `<`, `>`, `<=`, `>=`, or `~=`). Two examples are: `count < limit` and `(height - offset) >= 0`. Expressions may also include logical functions, as in: `isreal(A)`. Simple expressions can be combined by logical operators (`&`,`\|`,`~`) into compound expressions such as: `(count < limit) & ((height - offset) >= 0)`.
`statements`	One or more MATLAB statements to be executed only if the `expression` is true (or nonzero). See Examples for information about how nonscalar variables are evaluated.

Examples

Here is an example showing if, else, and elseif:

for i = 1:n
    for j = 1:n
        if i == j
            a(i,j) = 2;
        elseif abs([i j]) == 1
            a(i,j) = 1;
        else
            a(i,j) = 0;
        end
    end
end

Such expressions are evaluated as false unless every element-wise comparison evaluates as true. Thus, given matrices A and B:

A =                  B =
     1     0             1     1
     2     3             3     4

The expression:


`A < B`	Evaluates as false	Since `A(1,1)` is not less than `B(1,1)`.
`A < (B+1)`	Evaluates as true	Since no element of `A` is greater than the corresponding element of `B`.
`A & B`	Evaluates as false	Since `A(1,2) \| B(1,2)` is false.
`5 > B`	Evaluates as true	Since every element of `B` is less than `5`.