R help - Feb 2007 - fitting the gamma cumulative distribution function

Hi.

I have a vector of quantiles and a vector of probabilites that, when 
plotted, look very like the gamma cumulative distribution function.  I 
can guess some shape and scale parameters that give a similar result, 
but I'd rather let the parameters be estimated.  Is there a direct way 
to do this in R?

Thanks,

Tim.

week <- c(0,5,6,7,9,11,14,19,39)
fraction <- c(0,0.23279,0.41093,0.58198,0.77935,0.88057,0.94231,0.98583,1)
weeks <- 1:160/4
plot(weeks, pgamma(weeks,shape=6,scale=1.15),type="l")
points(week,fraction,col="red")

Hi Tim,

I believe fitdistr() in the MASS package is the function you are looking for.
(example given in help page)...

Best regards,
ST

--- Tim Bergsma <timb at metrumrg.com> wrote:
> Hi.
> 
> I have a vector of quantiles and a vector of probabilites that, when 
> plotted, look very like the gamma cumulative distribution function.  I 
> can guess some shape and scale parameters that give a similar result, 
> but I'd rather let the parameters be estimated.  Is there a direct way 
> to do this in R?
> 
> Thanks,
> 
> Tim.
> 
> week <- c(0,5,6,7,9,11,14,19,39)
> fraction <-
c(0,0.23279,0.41093,0.58198,0.77935,0.88057,0.94231,0.98583,1)
> weeks <- 1:160/4
> plot(weeks, pgamma(weeks,shape=6,scale=1.15),type="l")
> points(week,fraction,col="red")
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 


 
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