symfun

Create symbolic functions

Syntax

f(inputs) = formula

f = symfun(formula,inputs)

Description

f(inputs) = formula creates the symbolic function f. For example, f(x,y) = x + y. The symbolic variables in inputs are the input arguments. The symbolic expression formula is the body of the function f.

f = symfun(formula,inputs) is the formal way to create a symbolic function.

Examples

Create and Define Symbolic Functions

Define the symbolic function x + y. First, create the function by using syms. Then define the function.

syms f(x,y)
f(x,y) = x + y

f(x, y) =
x + y

Find the value of f at x = 1 and y = 2.

f(1,2)

ans =
3

Define the function again by using the formal way.

syms x y
f = symfun(x+y,[x y])

f(x, y) =
x + y

Return Body and Arguments of Symbolic Function

Return the body of a symbolic function by using formula. You can use the body for operations such as indexing into the function. Return the arguments of a symbolic function by using argnames.

Index into the symbolic function [x^2, y^4]. Since a symbolic function is a scalar, you cannot directly index into the function. Instead, index into the body of the function.

syms f(x,y)
f(x,y) = [x^2, y^4];

fbody = formula(f);
fbody(1)
fbody(2)

ans =
x^2
ans =
y^4

Return the arguments of the function.

fvars = argnames(f)

fvars =
[ x, y]

Input Arguments

formula — Function body

symbolic expression | vector of symbolic expressions | matrix of symbolic expressions

Function body, specified as a symbolic expression, vector of symbolic expressions, or matrix of symbolic expressions.

Example: x + y

inputs — Input argument or arguments of function

symbolic variable | array of symbolic variables

Input argument or arguments of a function, specified as a symbolic variable or an array of symbolic variables, respectively.

Example: [x,y]

Output Arguments

f — Function

symbolic function (symfun data type)

Function, returned as a symbolic function (symfun data type).