public void ToTaylorExpansion_1()
{
var ln = new LogarithmicFunction {
Aparam = 2, Bparam = 5
};
var expansion = ln.ToTaylorExpansion(5).ToList();
expansion.Should().HaveCount(7);
expansion.Select(s => s.PolynomialDegree).Should().ContainInOrder(0, 1, 2, 3, 4, 5, 0);
expansion.Select(s => s.LittleODegree).Should().ContainInOrder(0, 0, 0, 0, 0, 0, 5);
expansion[0].Coefficient.Should().BeApproximately(Math.Log(5), 1e-10);
expansion[1].Coefficient.Should().BeApproximately(0.4, 1e-10);
expansion[2].Coefficient.Should().BeApproximately(-0.16 / 2, 1e-10);
expansion[3].Coefficient.Should().BeApproximately(0.064 / 3, 1e-10);
expansion[4].Coefficient.Should().BeApproximately(-0.0256 / 4, 1e-10);
expansion[5].Coefficient.Should().BeApproximately(0.01024 / 5, 1e-10);
expansion[6].Coefficient.Should().BeApproximately(1.0, 1e-10);
}
public static IElementaryFunction ConvertToElementaryFunction(string str)
{
IElementaryFunction function = null;
double[] arr = null;
if (str.Contains("sin"))
{
function = new Sine();
arr = FindParameters(str.Substring(4, str.Count() - 4));
function.Aparam = arr[0];
function.Bparam = arr[1];
}
else if (str.Contains("cos"))
{
function = new Cosine();
arr = FindParameters(str.Substring(4, str.Count() - 4));
function.Aparam = arr[0];
function.Bparam = arr[1];
}
else if (str.Contains("ln"))
{
function = new LogarithmicFunction();
arr = FindParameters(str.Substring(3, str.Count() - 3));
function.Aparam = arr[0];
function.Bparam = arr[1];
}
else if (str.Contains("e^"))
{
function = new ExponentialFunction();
arr = FindParameters(str.Substring(3, str.Count() - 3));
function.Aparam = arr[0];
function.Bparam = arr[1];
}
else if (str.Contains(")^(") || str.Contains("x^(") || str.Contains(")^"))
{
function = new PowerFunction();
int powerPosition = 0;
for (int i = 0; i < str.Count(); i++)
{
if (str[i] == '^')
{
powerPosition = i;
StringBuilder num = new StringBuilder();
StringBuilder den = new StringBuilder();
bool slash = false;
for (int j = i + 1; j < str.Count(); j++)
{
if (str[j] != '/' && str[j] != '(' && str[j] != ')')
{
if (slash == false)
{
num.Append(str[j]);
}
else
{
den.Append(str[j]);
}
}
else if (str[j] == '/')
{
slash = true;
}
}
if (slash == false)
{
((PowerFunction)function).PowerDenominator = 1;
}
else
{
((PowerFunction)function).PowerDenominator = int.Parse(den.ToString());
}
((PowerFunction)function).PowerNumerator = int.Parse(num.ToString());
}
}
int beginPosition = 0;
if (str[0] == '(')
{
beginPosition = 1;
}
arr = FindParameters(str.Substring(beginPosition, powerPosition - beginPosition));
function.Aparam = arr[0];
function.Bparam = arr[1];
}
return(function);
}
