(PR#1007) [Rd] ks.test doesn't compute correct empirical

Full_Name: Andrew Grant McDowell
Version: R 1.1.1 (but source in 1.3.0 looks fishy as well)
OS: Windows 2K Professional (Consumer)
Submission from: (NULL) (194.222.243.209)

In article <xeQ_6.1949$xd.353840@typhoon.snet.net>,
johnt@tman.dnsalias.com writes

Can someone help?  In R, I am generating a vector of 1000 samples from
Bin (1000, 0.25).  I then do a Kolmogorov Smirnov test to test if the
vector has been drawn from a population of Bin (1000, 0.25).  I would
expect a reasonably high p-value.....

ks.gof(o, dist="binomial", size=100, prob=0.25)

Either I am doing something wrong in R, or I am misunderstanding how this
test should work (both quite possible)...


Thanks,
JT..

#### 1000 random samples from binomial dist with mean =.25, n=100...
o<-rbinom (1000, 100, .25)
mean (o);

[1] 25.178

var (o);

[1] 19.61193

ks.test (o, "pbinom", 100, .25);

       One-sample Kolmogorov-Smirnov test

data:  o
D = 0.0967, p-value = 1.487e-08
alternative hypothesis: two.sided



p-value is mighty small, leading me to reject the null hypothesis that
the sample has been drawn from the Bin(100, 0.25) distribution!!!

Some more oddities:

o<-rbinom(10000, 1, 0.25)
ks.test(o, "pbinom", 1, 0.25)

         One-sample Kolmogorov-Smirnov test

data:  o
D = 0.75, p-value = < 2.2e-16
alternative hypothesis: two.sided

length(o[o==0])

[1] 7491

length(o[o==1])

[1] 2509

o<-rep(0,10000)
ks.test(o, "pbinom", 1, 0.25)

         One-sample Kolmogorov-Smirnov test

data:  o
D = 0.75, p-value = < 2.2e-16
alternative hypothesis: two.sided

length(o[o==0])

[1] 10000

length(o[o==1])

[1] 0

Here zeroing out the data does not change the reported D value

ks.test(rep(1,10000), "pbinom", 1, 0.25)

After playing about with
ks.test(c(rep(0, X), rep(1, 1000-x)), "pbinom", 1, p)
for a bit I conjecture that ks.test() takes no account
whatsoever of ties, but merely sorts the input values
and looks for max (position/N - pbinom(value, 1, p)).
Anybody got the source handy?

After 30 minutes of download, the relevant part of ks.test.R would appear to be