From: Michael Rennie <mrennie_at_utm.utoronto.ca>

Date: Thu 29 Jul 2004 - 15:57:02 EST

Date: Thu 29 Jul 2004 - 15:57:02 EST

Hi, there

I am quite sure there is an easy answer to this, but I am unsure how to gather a bunch of t-statistics in an organized format.

I am trying to generate a list of t-statistics for a randomization routine. If I try to collect a bunch of t-statistics from a run, this is what happens:

> M <- 10 ; simt <- NULL

> for(i in 1:M)

*+ {
**+ perm<-sample(site,replace=F)
**+
**+ permute<-cbind(perm, site, a, b, c)
**+
**+ m<- order(perm)
**+
**+ m1<-cbind(perm[m], site[m], a[m], b[m], c[m])
**+
**+ black<-c((m1[1:5,5]),(m1[11:15,5]))
**+ #black
**+
**+ white<-c((m1[6:10,5]),(m1[16:20,5]))
**+ #white
**+
**+ sims <- t.test(black,white,var.equal=FALSE,mu=0)$statistic
**+ simt<-c(simt,sims)
*

+ #simt

+ } # Next i (next simulation)

>

> simt

t t t t t t t 0.3474150 0.1542973 -0.4044992 1.2466663 -0.2933944 -0.5809257 0.7799080

t t t

-1.4132713 1.2048335 -0.6596936

Which gives me a list, but not in a form that I can do anything with. This is in stark contrast to what happens when requesting p-values, which gives output like this:

M <- 10 ; simt <- NULL

> for(i in 1:M)

*+ {
**+ perm<-sample(site,replace=F)
**+
**+ permute<-cbind(perm, site, a, b, c)
**+
**+ m<- order(perm)
**+
**+ m1<-cbind(perm[m], site[m], a[m], b[m], c[m])
**+
**+ black<-c((m1[1:5,5]),(m1[11:15,5]))
**+ #black
**+
**+ white<-c((m1[6:10,29]),(m1[16:20,5]))
**+ #white
**+
**+ sims <- t.test(black,white,var.equal=FALSE,mu=0)$p.value
**+ simt<-c(simt,sims)
*

+ #simt

+ } # Next i (next simulation)

>

> simt

[1] 0.6763749 0.7480091 0.9447851 0.3342029 0.7852635 0.3199006 0.5272153
[8] 0.3863616 0.7333693 0.7268907

Now THAT'S what I'd like to get for my t-statistics- a nice vector (simt) that I can deal with later, rather than the output I am currently getting (the first output above).

Does anyone know a way to extract JUST the t-statistics from the t.test, without the "t" character header, so I can generate a nice little vector? Alternatively, can I manipulate the output I am currently getting for the tstatistics so that I can isolate just the numbers?

-- Michael Rennie Ph.D. Candidate University of Toronto at Mississauga 3359 Mississauga Rd. N. Mississauga ON L5L 1C6 Ph: 905-828-5452 Fax: 905-828-3792 ______________________________________________ R-help@stat.math.ethz.ch mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Thu Jul 29 16:05:27 2004

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