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Scilab Help >> Polynomials > varn

# varn

symbolic variable of a polynomial or a rational

### Syntax

```symb = varn(p)
pm = varn(p, varname)```

### Arguments

p

matrix of polynomials or of rationals. In Scilab, only univariate polynomials and rationals are supported. In a matrix, all polynomials or rationals have the same symbolic variable name.

symb, varname

Characters string: current or new name of the symbolic variable. Allowed characters are the same as for variables names (see naming rules).

pm

matrix of polynomials or of rationals, equal to `p`, with its variable name set to `varname`.

### Description

`symb=varn(p)` returns in `symb` the name of the symbolic variable of polynomials `p`.

`varn(p,'s')` returns a polynomial matrix with same coefficients as `p` but with `'s'` as symbolic variable (change of variable name).

`varn([])` yields [].

### Examples

With a matrix of polynomials:

```s = poly(0,'s'); p = [s , 1-s^2]
v = varn(p)
typeof(v)
px = varn(p,'x')
px == p```
```--> s = poly(0,'s'); p = [s , 1-s^2]
p  =
2
s   1 -s

--> v = varn(p)
v  =
s

--> typeof(v)
ans  =
string

--> px = varn(p,'x')
px  =
2
x   1 -x

--> px == p
ans  =
T T
```

With a matrix of rationals:

```f = %z/(%z-1); f = [f f^2]
varn(f)
fx = varn(f, "x")
fx == f```
```--> f = %z/(%z-1); f = [f f^2]
f  =
2
z          z
-------  -----------
2
-1 + z   1 - 2z + z

--> varn(f)
ans  =
z

--> fx = varn(f, "x")
fx  =
2
x          x
-------  -----------
2
-1 + x   1 - 2x + x

--> fx == f
ans  =
T T
```

### See also

• poly — Polynomial definition from given roots or coefficients, or characteristic to a square matrix.
• rlist — Scilab rational fraction function definition
• naming rules — Naming rules for variables and functions

### History

 Version Description 5.5.1 Extension to rationals 6.0.0 The name of the symbolic variable is no longer limited to 4 characters. It can now include extended UTF-8 characters. varn([]) now returns [] instead of routing to %s_varn().

### Comments

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