simple implementation of mathematic function erf "Error function", in JavaScript JavaScriptによる誤差関数の実装

erf.js

function erf(x){
    // erf(x) = 2/sqrt(pi) * integrate(from=0, to=x, e^-(t^2) ) dt
    // with using Taylor expansion, 
    //        = 2/sqrt(pi) * sigma(n=0 to +inf, ((-1)^n * x^(2n+1))/(n! * (2n+1)))
    // calculationg n=0 to 50 bellow (note that inside sigma equals x when n = 0, and 50 may be enough)
    var m = 1.00;
    var s = 1.00;
    var sum = x * 1.0;
    for(var i = 1; i < 50; i++){
        m *= i;
        s *= -1;
        sum += (s * Math.pow(x, 2.0 * i + 1.0)) / (m * (2.0 * i + 1.0));
    }  
    return 2 * sum / Math.sqrt(3.14159265358979);
}

See http://app.kcrt.net/med/#lmsvalue for sample application (in Japanese)