I used the function mix (package mixdist) to fit Gamma mixture distributions. The function gives mu and sigma parameters (output below). How can I find the scale and shape parameters ?

      pi    mu sigma 
1 0.2089 185.7 285.4 
2 0.7911 530.1 423.5 

1 Answer 1


Hint: Page 4 of the manual of the package indicates that mu represents the mean and sigma represents the standard deviation (square root of the variance):


Since the Gamma distribution has closed form mean and standard deviation, you can easily transformed into scale and shape:


  • 1
    $\begingroup$ From the link about Gamma distribution, mean = scale x shape. How can I find the scale and shape values from only the mean value ? $\endgroup$
    – Marine
    Commented Aug 26, 2016 at 13:33

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