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Maths › Approximation › Polynomial ›

Poly Eval

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Evaluates a polynomial of degree N.

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Contents

Interface
PolyEval
PolyEval1
Page Comments

Interface

C++

Overview

Evaluates polynomial of degree N:

$y = C_0 + C_1 x + C_2 x^2 + ... + C_N x^N$

(2)

Coefficients are stored in reverse order, i.e.

$coef[0] = C_N , ..., coef[N] = C_0$

(3)

PolyEval

doublepolyEval(	double	`x`
	const double*	`coef`
	int	`N`	)

Evaluates polynomial of degree N

Example:

The following code computes solutions to the polynomial

$f(x) = 3 + 2x + 1x^2$

(4)

#include <stdio.h>
#include <codecogs/maths/approximation/polynomial/poly_eval.h>
 
int main()
{
  using namespace Maths::Algebra::Polynomial;
  static double A[] = { 1,2,3 };
  for(int x=2;x<=5;x++)
    printf("\n polyEval(%d, A, 2)=%.1lf", x, polyEval(x, A, 2));
 
  return 0;
}

Output:

polyEval(2, A, 2)=11.0
polyEval(3, A, 2)=18.0
polyEval(4, A, 2)=27.0
polyEval(5, A, 2)=38.0

References:

Cephes Math Library Release 2.1: December, 1988

Note

In the interest of speed, there are no checks for out of bounds arithmetic.

Parameters

x	main variant
coef	array of coefficients <tt>coef[0..N]</tt> in reverse order
N	degree of polynomial, also one less that number of coefficients supplied.

Authors

Stephen L. Moshier Copyright 1984, 1987, 1988
Documentation by Will Bateman (August 2005)

Source Code

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PolyEval1

doublepolyEval1(	double	`x`
	const double*	`coef`
	int	`N`	)

Evaluates polynomial of degree N, where the coefficient $\inline C_N=1.0$ . i.e. coef[0] = 1.0,

$y = C_0 + C_1 x + C_2 x^2 + ... + x^N$

(5)