Question #63618
Make a javascript code for horner's rule polynomial evaluation
Expert's answer
Answer on Question #63618, Programming & Computer Science | JavaScript
Question:
Make a javascript code for Horner's rule polynomial evaluation
Solution:
function horner(coeffs, x) {
return coeffs.reduce( // Reduce means apply function (that passed as first argument) to the array from left to right
function (acc, coeff) { return (acc * x + coeff) },
0); // Initial value == 0
}
// evaluate polynomial at x=3
var x = 3;
// -19*x^7 + 17*x^6 - 13*x^5 + 11*x^4 - 7*x^3 + 5*x^2 - 3*x^1 + 2*x^0
var coeff = [-19, 17, -13, 11, -7, 5, -3, 2]
// Evaluate and print result
console.log(horner(coeff, x)); // ==> -31579Example test RUN within HTML page:
<!DOCTYPE > <head>
<head>
<title>Horner rule</title>
<script></script>
function horner(coeffs, x) {
return coeffs.reduce( // Reduce means apply function (that passed as first argument) to the array from left to right
function(acc, coeff) { return(acc * x + coeff) },
0); // Initial value == 0
}
// evaluate polynomial at x=3
var x = 3;
// -19*x^7 + 17*x^6 - 13*x^5 + 11*x^4 - 7*x^3 + 5*x^2 - 3*x^1 + 2*x^0
var coeff = [-19,17,-13,11,-7,5,-3,2]
// Evaluate and print result
console.log(horner(coeff, x)); // ==> -31579
function printPoly(coeff) {
s = ''
for(var i = 0; i < coeff.length; ++i) {
if( coeff[i] == 0 ) continue;
s += (coeff[i] > 0 ? "+" : "") + coeff[i] + "*x^" + (coeff.length - i - 1);
}
return s;
}
function run() {
var coeff = prompt("Enter polynomial coefficients (from highest to lowest degree) separated by coma: ", "-19,17,-13,11,-7,5,-3,2").split(",")
var x = prompt("Enter point at witch you want to evaluate your polynomial, x=", "3");
for(var i = 0; i < coeff.length; ++i) {
coeff[i] = parseInt(coeff[i], 10);
}
document.write("Your polynomial: " + printPoly(coeff) + "<br>");
document.write("Your point x=" + x + "<br>");
document.write("Evaluation result=" + horner(coeff, x) + "<br>");
}
</script>
</head>
<body onload="run();">
</body>
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