[R] (no subject)

[William Dunlap]

> fitdistr(y, "chi-squared", start = list(4), method = "Brent", lower=0.9, upper=3)

First, it would  be nice if your mail had a subject line and you showed
the error message you got from this command.
I got:
  > z <- fitdistr(y, "chi-squared", start = list(4), method="Brent", lower=0.9, upper=3)
  > z
  Error in dn[[2L]] : subscript out of bounds
  > str(z)
  List of 5
   $ estimate: num 1
   $ sd      : num 0.00286
   $ vcov    : num [1, 1] 8.16e-06
   $ loglik  : num -79007
   $ n       : int 100000
   - attr(*, "class")= chr "fitdistr"
showing that the error was in the printing of the result, not in computing
the result.

There are a few problems here.  First, the print method assumes that the
optimizer attaches parameter names to the parameter vector.  Second,
optim(method="Brent") does not attach a name to its output parameter the
way the other optimization method do (I suppose that is because it only
works on univariate problems.)  Third, you didn't supply a parameter name
in 'start'.

You can get a printable answer by using the default method and supplying
a name for the parameter.
   > zz <- fitdistr(y, "chi-squared", start = list(df=4), lower=0.9, upper=3)
   > zz
          df     
     1.003840114 
    (0.002856363)
   > str(zz)
   List of 5
    $ estimate: Named num 1
     ..- attr(*, "names")= chr "df"
    $ sd      : Named num 0.00286
     ..- attr(*, "names")= chr "df"
    $ vcov    : num [1, 1] 8.16e-06
     ..- attr(*, "dimnames")=List of 2
     .. ..$ : chr "df"
     .. ..$ : chr "df"
    $ loglik  : num -79007
    $ n       : int 100000
    - attr(*, "class")= chr "fitdistr"

By the way, giving a starting value that is not between the upper and lower
limits that you also gave is asking for trouble of a different sort.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Jim Silverton
> Sent: Tuesday, November 19, 2013 4:30 PM
> To: r-help at r-project.org
> Subject: [R] (no subject)
> 
> I generated some random data using R and then trying to see if it came from
> the same distribution but the erros keep piling.  Can anyone help?
> 
> 
> 
> y=rchisq(100000,1)
> mean(y)
> var(y)
> library(MASS)
> fitdistr(y, "chi-squared", start = list(4), method = "Brent", lower=0.9,
> upper=3)
> 
> 
> --
> Thanks,
> Jim.
> 
> 	[[alternative HTML version deleted]]
> 
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