symType

Determine type of symbolic object

Syntax

s = symType(symObj)

Description

s = symType(symObj) returns the type of a symbolic object. For example, symType(sym('x')) returns "variable".

Examples

Symbolic Number

Create a symbolic number and determine its type.

a = sym('3/9');
s = symType(a)

s = 
"rational"

Now construct a symbolic array by including symbolic numbers in the array elements. Determine the symbolic type of each array element.

B = [-5, a, vpa(a), 1i, pi];
s = symType(B)

s = 1×5 string
    "integer"    "rational"    "vpareal"    "complex"    "constant"

Symbolic Function or Expression

Create a symbolic function f(x) using syms.

syms f(x)

Determine the type of the function. Because f(x) is an unassigned symbolic function, it has the symbolic type "symfun".

s = symType(f)

s = 
"symfun"

Assigning a mathematical expression to f(x) changes its symbolic type.

f(x) = x^2;
s = symType(f)

s = 
"expression"

Now check the symbolic type of f(x) = x and its derivative.

f(x) = x;
s = symType(f)

s = 
"variable"

s = symType(diff(f))

s = 
"integer"

Inequalities and Solutions

Determine the type of various symbolic objects when solving for inequalities.

Create a quadratic function.

syms y(x)
y(x) = 100 - 5*x^2

y(x) = $$100-5\hspace{0.17em}{x}^2$$

Set two inequalities to the quadratic function. Check the symbolic type of each inequality.

eq1 = y(x) > 10;
eq2 = x > 2;
s = symType([eq1 eq2])

s = 1×2 string
    "equation"    "equation"

Solve the inequalities using solve. Return the solutions by setting 'ReturnConditions' to true.

eqSol = solve([eq1 eq2], 'ReturnConditions', true);
sols = eqSol.conditions

sols = $$x<\sqrt{18}\wedge 2<x$$

Determine the symbolic type of the solutions.

s = symType(sols)

s = 
"logicalexpression"

Input Arguments

symObj — Symbolic objects

symbolic numbers | symbolic variables | symbolic expressions | symbolic functions | symbolic units

Symbolic objects, specified as symbolic numbers, symbolic variables, symbolic expressions, symbolic functions, or symbolic units.

Output Arguments

s — Symbolic types

string array

Symbolic types, returned as a string array. This table shows output values for various symbolic objects.

Output	Description	Input Example
"integer"	symbolic integer number	symType(sym('-1'))
"rational"	symbolic rational number	symType(sym('1/2'))
"vpareal"	symbolic variable-precision floating-point real number	symType([sym('1.5') vpa('3/2')])
"complex"	symbolic complex number	symType(sym('1+2i'))
"constant"	symbolic mathematical constant	symType(sym([pi catalan]))
"variable"	symbolic variable	syms x; symType(x)
"symfun"	unassigned symbolic function	syms f(x); symType(f)
"expression"	symbolic expression	syms x; symType(sqrt(x))
"equation"	symbolic equation and inequality	syms x; symType(x>=0)
"unit"	symbolic unit	symType(symunit('meter'))
"logicalexpression"	symbolic logical expression	syms x y; symType(x|y)
"logicalconstant"	symbolic logical constant	symType([symtrue symfalse])
"unsupported"	symbolic object not supported by symType

Version History

Introduced in R2019a