# findSymType

Find symbolic subobjects of specific type

## Syntax

``X = findSymType(symObj,type)``
``X = findSymType(symObj,funType,vars)``

## Description

example

````X = findSymType(symObj,type)` returns a vector of symbolic subobjects of type `type` from the symbolic object `symObj`. The input `type` must be a case-sensitive string scalar or character vector, and it can include a logical expression. If `symObj` does not contain a symbolic subobject of type `type`, then `findSymType` returns an empty scalar.If `symObj` contains several subexpressions of type `type`, then `findSymType` returns the largest matching subexpression. ```

example

````X = findSymType(symObj,funType,vars)` returns a vector of unassigned symbolic functions that depend on the variables `vars` from the symbolic input `symObj`.You can set the function type `funType` to `'symfunOf'` or `'symfunDependingOn'`. For example, `syms f(x); findSymType(f,'symfunOf',x)` returns `f(x)`.```

## Examples

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Find and return specific symbolic numbers and constants in a symbolic expression.

Create a symbolic expression.

`expr = sym('1/2')*pi + vpa(pi)`
```expr =  $\frac{\pi }{2}+3.1415926535897932384626433832795$```

Find symbolic numbers of type `'integer'`.

`X = findSymType(expr,'integer')`
`X = $\left(\begin{array}{cc}1& 2\end{array}\right)$`

Find symbolic numbers of type `'integer | real'`.

`X = findSymType(expr,'integer | real')`
```X =  $\left(\begin{array}{cc}\frac{1}{2}& 3.1415926535897932384626433832795\end{array}\right)$```

Find symbolic numbers of type `'vpareal'`.

`X = findSymType(expr,'vpareal')`
`X = $3.1415926535897932384626433832795$`

Find symbolic numbers of type `'complex'`.

`X = findSymType(expr,'complex')`
``` X = Empty sym: 1-by-0 ```

The `findSymType` function returns an empty scalar since the expression `expr` does not contain any complex numbers.

Now find symbolic constant of type `'constant'`.

`X = findSymType(expr,'constant')`
```X =  $\frac{\pi }{2}+3.1415926535897932384626433832795$```

When there are several subexpressions of type `'constant'`, `findSymType` returns the largest matching subexpression.

Find and return symbolic variables and functions in a symbolic equation.

Create a symbolic equation.

```syms y(t) k eq = diff(y) + k*y == sin(y)```
```eq(t) =  ```

Find symbolic variables of type `'variable'` in the equation.

`X = findSymType(eq,'variable')`
`X = $\left(\begin{array}{cc}k& t\end{array}\right)$`

Find an unassigned symbolic function of type `'symfun'` in the equation.

`X = findSymType(eq,'symfun')`
`X = $y\left(t\right)$`

Find a symbolic math function of type `'diff'` in the equation.

`X = findSymType(eq,'diff')`
```X =  ```

Find and return symbolic functions with specific variable dependencies in an expression.

Create a symbolic expression.

```syms n f(x) g(x) y(x,t) expr = x + f(x^n) + g(x)+ y(x,t)```
`expr = $x+f\left({x}^{n}\right)+g\left(x\right)+y\left(x,t\right)$`

Find unassigned symbolic functions of type `'symfun'` in the expression.

`X = findSymType(expr,'symfun')`
`X = $\left(\begin{array}{ccc}f\left({x}^{n}\right)& g\left(x\right)& y\left(x,t\right)\end{array}\right)$`

Find symbolic functions that depend on the exact sequence of variables `[x t]` using `'symfunOf'`.

`X = findSymType(expr,'symfunOf',[x t])`
`X = $y\left(x,t\right)$`

Find symbolic functions that have a dependency on the variable x using `'symfunDependingOn'`.

`X = findSymType(expr,'symfunDependingOn',x)`
`X = $\left(\begin{array}{cc}g\left(x\right)& y\left(x,t\right)\end{array}\right)$`

## Input Arguments

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

Symbolic types, specified as a case-sensitive scalar string or character vector. The input `type` can contain a logical expression. The value options follow.

Symbolic Type CategoryString Values
numbers
• `'integer'` — integer numbers

• `'rational'` — rational numbers

• `'vpareal'` — variable-precision floating-point real numbers

• `'complex'` — complex numbers

• `'real'` — real numbers, including `'integer'`, `'rational'`, and `'vpareal'`

• `'number'` — numbers, including `'integer'`, `'rational'`, `'vpareal'`, `'complex'`, and `'real'`

constants`'constant'` — symbolic mathematical constants, including `'number'`
symbolic math functions`'vpa'`, `'sin'`, `'exp'`, and so on — symbolic math functions in symbolic expressions
unassigned symbolic functions
• `'F'`, `'g'`, and so on — function name of an unassigned symbolic function

• `'symfun'` — unassigned symbolic functions

arithmetic operators
• `'plus'` — addition operator `+` and subtraction operator `-`

• `'times'` — multiplication operator `*` and division operator `/`

• `'power'` — power or exponentiation operator `^` and square root operator `sqrt`

variables`'variable'` — symbolic variables
units`'unit'` — symbolic units
expressions`'expression'` — symbolic expressions, including all of the preceding symbolic types
logical expressions
• `'or'` — logical OR operator `|`

• `'and'` — logical AND operator `&`

• `'not'` — logical NOT operator `~`

• `'xor'` — logical exclusive-OR operator `xor`

• `'logicalconstant'` — symbolic logical constants `symtrue` and `symfalse`

• `'logicalexpression'` — logical expressions, including `'or'`, `'and'`, `'not'`, `'xor'`, `symtrue` and `symfalse`

equations and inequalities
• `'eq'` — equality operator `==`

• `'ne'` — inequality operator `~=`

• `'lt'` — less-than operator `<` or greater-than operator `>`

• `'le'` — less-than-or-equal-to operator `<=` or greater-than-or-equal-to operator `>=`

• `'equation'` — symbolic equations and inequalities, including `'eq'`, `'ne'`, `'lt'`, and `'le'`

unsupported symbolic types

`'unsupported'` — unsupported symbolic types

If `symObj` contains several subexpressions of type `type`, then `findSymType` returns the largest matching subexpression (topmost matching node in a tree data structure).

Function type, specified as `'symfunOf'` or `'symfunDependingOn'`.

• `'symfunOf'` finds and returns the unassigned symbolic functions that depend on the exact sequence of variables specified by the array `vars`. For example, ```syms f(x,y); findSymType(f,'symfunOf',[x y])``` returns `f(x,y)`.

• `'symfunDependingOn'` finds and returns the unassigned symbolic functions that have a dependency on the variables specified by the array `vars`. For example, ```syms f(x,y); findSymType(f,'symfunDependingOn',x)``` returns `f(x,y)`.

Input variables, specified as symbolic variables or a symbolic array.

## Version History

Introduced in R2019a