public static double GetCosineDistanceByChar(this string str1, string str2)
{
if (str1 == null || str2 == null)
{
return(1);
}
if (str1.Equals(str2))
{
return(0);
}
var cs1 = str1.ToCharArray();
var cs2 = str2.ToCharArray();
IDictionary <char, double> freq1 = new SortedDictionary <char, double>();
foreach (var c in cs1.Concat(cs2))
{
freq1.AddOrUpdateValue(c, 0);
}
IDictionary <char, double> freq2 = new SortedDictionary <char, double>(freq1);
var groupedCs1 = cs1.GroupBy(c => c);
foreach (var charGroup in groupedCs1)
{
freq1[charGroup.Key] = charGroup.Count();
}
var groupedCs2 = cs2.GroupBy(c => c);
foreach (var charGroup in groupedCs2)
{
freq2[charGroup.Key] = charGroup.Count();
}
var distance = Distance.Cosine(freq1.Values.ToArray(), freq2.Values.ToArray());
return(distance.Equals(double.NaN) ? 1 : distance);
}