lcoeff

Leading coefficient of a polynomial

Use only in the MuPAD Notebook Interface.

This functionality does not run in MATLAB.

Syntax

lcoeff(p, <order>)
lcoeff(f, <vars>, <order>)

Description

lcoeff(p) returns the leading coefficient of the polynomial p.

The returned coefficient is "leading" with respect to the lexicographical ordering, unless a different ordering is specified via the argument order. Cf. Example 1.

A polynomial expression f is first converted to a polynomial with the variables given by vars. If no variables are given, they are searched for in f. See poly about details of the conversion. The result is returned as polynomial expression. FAIL is returned if f cannot be converted to a polynomial. Cf. Example 3.

The result of lcoeff is not fully evaluated. Evaluation can be enforced by the function eval. Cf. Example 2.

Examples

Example 1

We demonstrate how various orderings influence the result:

p := poly(5*x^4 + 4*x^3*y*z^2 + 3*x^2*y^3*z + 2, [x, y, z]):
lcoeff(p), lcoeff(p, DegreeOrder), lcoeff(p, DegInvLexOrder)

The following call uses the reverse lexicographical order on 3 indeterminates:

lcoeff(p, Dom::MonomOrdering(RevLex(3)))

delete p:

Example 2

The result of lcoeff is not fully evaluated:

p := poly(a*x^2 + 27*x, [x]): a := 5:
lcoeff(p), eval(lcoeff(p))

delete p, a:

Example 3

The expression 1/x may not be regarded as polynomial:

lcoeff(1/x)

Parameters

p

A polynomial of type DOM_POLY

f

A polynomial expression

vars

A list of indeterminates of the polynomial: typically, identifiers or indexed identifiers

order

The term ordering: either LexOrder, or DegreeOrder, or DegInvLexOrder, or a user-defined term ordering of type Dom::MonomOrdering. The default is the lexicographical ordering LexOrder.

Return Values

Element of the coefficient domain of the polynomial or FAIL.

Overloaded By

p

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