normalPdf function
Normal probability density function.
Throws an error of type ErrorOfType<InvalidFunctionParameter>
if stdDev < 0
.
Implementation
double normalPdf(num x, num mean, num stdDev) {
if (stdDev <= 0.0) {
throw throw ErrorOfType<InvalidFunctionParameter>(
invalidState: 'stdDev: $stdDev <= 0.',
expectedState: 'stdDev > 0',
);
}
final invStdDev = 1.0 / stdDev;
x = (x - mean) * invStdDev;
return invSqrt2Pi * invStdDev * math.exp(-0.5 * x * x);
}