[R] testing exponential distributions

[Christian Jost]

Dear all,

I try to test behavioural data durations whether they follow an 
exponential distribution. My data have the particularity that there 
are no values below a certain threshold, and the only test adapted to 
this case I could find is the Shapiro-Wilk test for exponentiality 
(Shapiro & Wilk 1972, Technometrics 14, 355-370). But it requires to 
compute Shapiro and Wilks critical W values. Is there any R function 
that lets me compute these values? I checked out the shapiro.test 
source which seems to compute these values in swilk.c, but I could 
not find an R function wrapper that would compute either these 
critical values for a given alpha and n (number of values) or a 
function that comptues directly the p-value for a given value of the 
W statistic and n. Any idea where I could find that? Or are there 
specific packages that let me test for exponentiality (tried package 
"survival", but my stat level seems to be too low to understand 
application of this package beyond simple survival curve 
visualisation).

Thanks for any help, Christian.