if (MATLAB Function Reference)

if	Examples See Also

Conditionally execute statements

Syntax

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`.