1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Regression Analysis for a Gamma function

  1. Jan 19, 2008 #1
    [SOLVED] Regression Analysis for a Gamma function

    My regression analysis program that I developed in BASICS back in the 1980's applies for half a dozen linear equations some of which are transormed into log forms. I would like to modify my program to include this Gamma function: I(t)=P*(t^s)*(e^(-ft)) which I can transform into this equivalent non- linear log form: Ln I(t)=Ln P + s*Ln t + (-ft); P,s and f are constants; t if for time; I(t) has for units cu.ft/sec or cu.m./sec. Is there any way to take care of the term (-ft). I got 18 data points available for this regression .

    I am not looking forward to trial and error to determine the constants P,s and f.

    Here is another thought. Since I have 18 data points (flow vs time), can I solve theses constants with matrices using this transformation: Ln I(t)=Ln P + s*Ln t + (-ft) eventho I would have 18 rows and and only 4 columns?
  2. jcsd
  3. Jan 19, 2008 #2
    Note, my request is not homework. This is a real situation involving a flooding situation arising from tropical storm Tammy back in 2005.
  4. Jan 19, 2008 #3


    User Avatar
    Science Advisor
    Homework Helper

    Why not run the regression y(t) = a + b1 x1(t) + b2 x2(t) + error, where y = log I, x1 = log t, x2 = t, and the parameters are a = Log P, b1 = s, b2 = -f?
  5. Jan 20, 2008 #4
    Yeah, I see what you mean. Instead of one independent variable, I'll two in that transformed equation. Thx.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Regression Analysis for a Gamma function
  1. Regression analysis? (Replies: 11)