When I saw your note late yesterday, I assumed that I had simply been an idiot and my problem really was as simple as a typo. However, when I had a chance to test it, I find:

RStudio:

fit2 <- fitdistr( x, "rayleigh", start = list(sigma = 1) )

Error in fitdistr(x, "rayleigh", start = list(sigma = 1)) :

unsupported distribution

fit2 <- fitdistr( x, "binom", start = list(sigma = 1) )

Error in fitdistr(x, "binom", start = list(sigma = 1)) :

unsupported distribution

fit2 <- fitdist( x, "rayleigh", start = list(sigma = 1) )

Error in checkparamlist(arg_startfix$start.arg, arg_startfix$fix.arg, :

'start' must specify names which are arguments to 'distr'.

fit2 <- fitdist( x, "binom", start = list(sigma = 1) )

Error in checkparamlist(arg_startfix$start.arg, arg_startfix$fix.arg, :

'start' must specify names which are arguments to 'distr'.

R terminal:

fit2 <- fitdistr( x, "rayleigh", start = list(sigma = 1) )

Error in fitdistr(x, "rayleigh", start = list(sigma = 1)) :

unsupported distribution

fit2 <- fitdistr( x, "binom", start = list(sigma = 1) )

Error in fitdistr(x, "binom", start = list(sigma = 1)) :

unsupported distribution

fit2 <- fitdist( x, "rayleigh", start = list(sigma = 1) )

fit2 <- fitdist( x, "binom", start = list(sigma = 1) )

Error in checkparamlist(arg_startfix$start.arg, arg_startfix$fix.arg, :

'start' must specify names which are arguments to 'distr'.

Again, the R Terminal can do the Rayleigh fit using fitdist while RStudio cannot...

And thanks for your help and patience.