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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

• 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().