public static double Sigma(string Expression, double LowerIndex, double UpperIndex, char IterationVariable, double Step)
{
double Result = 0;
var parser = new MathParser();
var Var = new Variable();
parser.Variables.Add(IterationVariable.ToString(), Var);
parser.Parse(Expression);
for (double i = LowerIndex; i <= UpperIndex; i += Step)
{
Var.Value = i;
Result += parser.Evaluate();
}
return Result;
}
public static double Integral(string Expression, double LowerIndex, double UpperIndex, char IterationVariable, int Kind)
{
var parser = new MathParser();
var Var = new Variable();
parser.Variables.Add(IterationVariable.ToString(), Var);
parser.Parse(Expression);
Func<double,double> proc = (x) =>
{
Var.Value = x;
return parser.Evaluate();
};
if (Kind == 0) return Integration.Trapezoidal(LowerIndex, UpperIndex, proc);
else if (Kind == 1) return Integration.LeftHand(LowerIndex, UpperIndex, proc);
else return Integration.MidPoint(LowerIndex, UpperIndex, proc);
}