Dear Developers Team,

I have two items:

1. wilcox.test with the paired=T option appears to delete zeros

before ranking absolute differences.

Would it be possible to add the feature of removing

zeros after ranking, which is given in Lehmann's Nonparametrics

as the preferred choice. See also Pratt (1959), JASA 54, 655-667.

It is given in wilcoxsign_test of the coin package as an

option through the argument ties="Pratt" as opposed to

ties="HollanderWolfe" (default). I understand this this might

be more difficult for wilcox.test because of the method

for calculating the null distribution.

2. For the following two samples

Augmenters <- c(17.94,13.32,11.31,10.62,7.56,

5.73,5.61,5.40,3.30,3.09,.93)

Reducers <- c(7.74,5.04,1.68,0.0,-3.03,-3.09,-10.53)

I get the following strange confidence percentage of 91.46556

together with a warning message, when asking for a 95% lower bound.

I had the impression that wilcox.test would only echo back the input

confidence level.

When I ask for a 90% interval I get the same correct lower bound

without the strange percentage and without warnings. The actual

confidence coefficient of the lower bound 3.09 is 0.9573

(conservatively) and one gets lower bound 3.3 with confidence

coefficient 0.9479 if the achievable confidence level closest to

.95 is desired.

wilcox.test(Augmenters,Reducers,conf.int=T,conf.level=.95,alternative="greater",exact=T)

Wilcoxon rank sum test

data: Augmenters and Reducers

W = 66, p-value = 0.005688

alternative hypothesis: true location shift is greater than 0

91.46556 percent confidence interval:

3.09 Inf

sample estimates:

difference in location

7.56

Warning message:

In switch(alternative, two.sided = { : Requested conf.level not

achievable

wilcox.test(Augmenters,Reducers,conf.int=T,conf.level=.9,alternative="two.sided",exact=T)

Wilcoxon rank sum test

data: Augmenters and Reducers

W = 66, p-value = 0.01138

alternative hypothesis: true location shift is not equal to 0

90 percent confidence interval:

3.09 13.62

sample estimates:

difference in location

7.56

Thanks very much for any help or fix, especially with regard to

item 2.

Fritz Scholz

fscholz at u.washington.edu