Calculate colour temperature in K

Question

I have written a lib for working with colours and stuck trying to calculate Tc(k). From what I have read working in the CIE 1931 XYZ colour space i

Answer 1

Based on the Wikipedia article I entered the approximated formula for Color Temperature calculation into Excel as

=(-449*((R1-0,332)/(S1-0,1858))^3)+(3525*((R1-0,332)/(S1-0,1858))^2)-(6823,3*((R1-0,332)/(S1-0,1858)))+(5520,33)

R1 is color space x coordinate from 0 to 1
S1 is color space y coordinate from 0 to 1

Works fine!