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> ## a quick check on vcov for fitdistr (from 7.3-6/7)
> 
> library(MASS)
> 
> options(digits=4)
> set.seed(1)
> x <- rnorm(100)
> fit <- fitdistr(x, "normal")
> fit
    mean       sd   
  0.10889   0.89370 
 (0.08937) (0.06319)
> vcov(fit)
         mean       sd
mean 0.007987 0.000000
sd   0.000000 0.003993
> 
> x <- rlnorm(100)
> fit <- fitdistr(x, "lognormal")
> fit
   meanlog     sdlog  
  -0.03781    0.95308 
 ( 0.09531) ( 0.06739)
> vcov(fit)
         meanlog    sdlog
meanlog 0.009084 0.000000
sdlog   0.000000 0.004542
> 
> x <- rpois(100, 4.5)
> fit <- fitdistr(x, "poisson")
> fit
   lambda 
  4.5400  
 (0.2131) 
> vcov(fit)
       lambda
lambda 0.0454
> 
> x <- rexp(100, 13)
> fit <- fitdistr(x, "exponential")
> fit
    rate 
  15.224 
 ( 1.522)
> vcov(fit)
      rate
rate 2.318
> 
> x <- rgeom(100, 0.25)
> fit <- fitdistr(x, "geometric")
> fit
    prob  
  0.22831 
 (0.02006)
> vcov(fit)
          prob
prob 0.0004022
>