`has`

Tests whether a symbolic expression contains a given subexpression.

Category: Symbolic Computations in MATLAB > Symbolic Variables, Expressions, Functions, and Preferences

Syntax

tf = has(expr, sub)

Returns true when sub occurs inside expr.

Description

has searches the whole expression tree, so has(x^2 + y, y) is true even though y is only one term of a sum. It matches structure, not value, so has(2*x, x) is true while has(x^2, 4) is false.

A typical use is deciding whether an expression still depends on a variable before differentiating or solving for it.

Input arguments

expr: Scalar symbolic expression to search.
sub: Variable or subexpression to look for.

Output arguments

tf: Logical scalar.

Example

Does the expression depend on a variable

syms x y
has(x^2 + y, y)
has(sin(x)*2, y)
has(sin(x)*2, sin(x))

Output

ans = logical
   1
ans = logical
   0
ans = logical
   1

Notes

In MatLivre sub must be a scalar symbolic expression; passing a symbolic array as sub raises an error. expr may be an array.

has