assumptions

Show assumptions set on symbolic variable

Syntax

Description

example

assumptions(var) returns all assumptions set on variable var.

example

assumptions returns all assumptions set on all variables in MATLAB® Workspace.

Examples

Assumptions on Several Variables

Show the assumptions set on variables n and x separately, and then show assumptions set on all variables.

Assume that the variable n is integer and the variable x is rational. In addition to that , assume that the product n*x belongs to the interval from -100 to 100:

syms n x
assume(n,'integer')
assume(x,'rational')
assumeAlso(-100 <= n*x <= 100)

To see the assumptions set on the variable n, enter:

assumptions(n)
ans =
[ -100 <= n*x, n*x <= 100, in(n, 'integer')]

The syntax in(n, 'integer') indicates n is an integer.

To see the assumptions set on the variable x, enter:

assumptions(x)
ans =
[ -100 <= n*x, n*x <= 100, in(x, 'rational')]

To see the assumptions set on all variables, use assumptions without any arguments:

assumptions
ans =
[ -100 <= n*x, n*x <= 100, in(n, 'integer'), in(x, 'rational')]

For further computations, clear the assumptions:

syms n x clear

Multiple Assumptions on One Variable

Show the assumptions set by using syms and assume.

Use assumptions to return all assumptions, including those set by the syms command:

syms x real
assumeAlso(x < 0)
assumptions(x)
ans =
[ x < 0, in(x, 'real')]

The syntax in(x, 'real') indicates x is real.

Input Arguments

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var — Variable for which to show assumptionssymbolic variable | array of symbolic variables | vector of symbolic variables | matrix of symbolic variables

Variable for which to show assumptions, specified as a symbolic variable or array, vector, or matrix of symbolic variables.

More About

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Tips

  • When you delete a symbolic object from the MATLAB workspace by using clear, all assumptions that you set on that object remain in the symbolic engine. If later you declare a new symbolic variable with the same name, it inherits these assumptions.

  • To clear all assumptions set on a symbolic variable var and the value of the variable, use this command:

     syms var clear
  • To clear assumptions and keep the value of the variable, use this command:

    sym('var','clear')
  • To clear all objects in the MATLAB workspace and close the MuPAD® engine associated with the MATLAB workspace resetting all its assumptions, use this command:

    clear all
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