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I am trying to write a function that will solve a simple system of nonlinear equations for the parameters that describe the beta distribution (a,b) given the mean and variance. mean = a/(a+b) variance = (a*b)/(((a+b)^2) * (a+b+1)) Any help as to where to start would be welcome. -- Scott Story Graduate Student MSU Ecology Department 319 Lewis Hall Bozeman, Mt 59717 406.994.2670 sstory at

Thanks to Gabor, Duncan, and Peter. I knew the answer had something to do with solving for a and b in terms of mean and variance. I will build a function using the equations you provided Duncan and will look into using Mathomatic in the future Gabor. Appreciate the help. Peter, this was not homework but I understand your concern. I don't use listserves that often but they do open a whole

I am trying to mimic the SAS code below in R. The trick is that each row in the dataset has variable "t" which controls how many times the do-loop below will be iterated (that is, the model is fit to the response, ifate, 0 to t-1 times for each row of data). Is it possible to incorporate a loop like this into nlme by writing a function? Can anybody provide some hints to get me on my