how to transpose a matrix in r if the usual `t( )` doesn't work?

Question

I have a matrix I am trying to transpose in R but the t() function does not return the right answer. How can I transpose the matrix?

> xx=matrix(c(3,7,4,8),2,byrow=TRUE)
> xx
     [,1]  [,2]
[1,]    3     7
[2,]    4     8
> t(xx)
[1] 0.7071068 0.7071068

i.e. as something like `t <- function(...) rep(sqrt(.5), 2)` — Josh O'Brien, Nov 26 '12 at 22:27
Thanks to you all, the problem has been solved now....:)..I used rm() function — user1854786, Nov 26 '12 at 22:37
@JoshO'Brien - That's a ridiculous suggestion... nobody would write that function... Clearly it was `t <- function(x){apply(x, 2, sd)} ` — Dason, Nov 26 '12 at 22:44
@JoshO'Brien : why did you delete your answer? Looked good to me .. — Ben Bolker, Nov 26 '12 at 23:11
@BenBolker -- 'cause it was wrong -- both parts of it! (That said, I'll undelete it: (a) as a monument to the stupidity of **guarantee**ing anything; and (b) because it's wrong in interesting ways.) — Josh O'Brien, Nov 26 '12 at 23:20

score 12 · Answer 1 · edited Nov 27 '12 at 02:39

This answer is incorrect, but in ways that were enlightening to me and might be to others, so I'll leave it up.

As @mnel noted, the base R function t() must be masked by another function of the same name. Try removing the function t() and doing t(xx) again. I guarantee you'll get the correct results.

What do you get when you run this:

rm(t)
t(xx)

If (despite my guarantee!) it still doesn't work, you can fully specify the version of t() you want to use, like this:

base::t(xx)

Here's why the two suggestions above are insufficient

From ?UseMethod:

Namespaces can register methods for generic functions. To support this, ‘UseMethod’ and ‘NextMethod’ search for methods in two places: first in the environment in which the generic function is called, and then in the registration data base for the environment in which the generic is defined (typically a namespace). So methods for a generic function need to be available in the environment of the call to the generic, or they must be registered. (It does not matter whether they are visible in the environment in which the generic is defined.)

I wrongly assumed that S3 method dispatch looks for methods like t.default() first in base:::.__S3MethodsTable__. and then perhaps in asNamespace("base")before looking in the calling environment, whereas the reverse is closer to the truth.

Edit from GSee

Here's an interactive session to demonstrate what could have been the problem.

> t <- function(x, ...) print("generic masked")
> t.default <- function(x, ...) print("t.default masked")
> t.matrix <- function(x, ...) print("t.matrix was used")
> t.numeric <- function(x, ...) print("t.numeric was used")
> xx=matrix(c(3,7,4,8),2,byrow=TRUE)
> t(xx)
[1] "generic masked"
> base::t(xx)
[1] "t.matrix was used"
> rm(t.matrix)
> base::t(xx)
[1] "t.numeric was used"
> rm(t.numeric)
> base::t(xx)
[1] "t.default masked"
> rm(t.default)
> base::t(xx)
     [,1] [,2]
[1,]    3    4
[2,]    7    8

That doesn't help if `t.default` is masked... or if there is a `t.matrix` method defined. ;-) — GSee, Nov 26 '12 at 22:33
@GSee -- It should help. `base::t(xx)` should look first in `asNamespace("base")`, where it'll find `t.default()` even if a function of the same name is registered elsewhere, right? — Josh O'Brien, Nov 26 '12 at 22:40
Thank you both, but actually i am trying to generate a chi-square plot. The function i defined is qqplot<-function (xx) { n=length(xx[,1]);p=length(xx[1,]) xbar=colMeans(as.data.frame(xx));ss=var(xx) ssinv=solve(ss);d2=c() for (i in (1:n)){ xi=cbind(xx[i,]-xbar) d2=c(d2,t(xi)%*%ssinv%*%xi) } q=qchisq(((1:n)-0.5)/n,p) plot(q,sort(d2),type="p",pch=20,col="red",xlab="q",ylab="d^2",main="Chi-squa re Quantile Plot") } — user1854786, Nov 26 '12 at 22:43
+1 for that point of widsom from Gsee on searching the globalenv first. Didn't know that. — Brandon Bertelsen, Nov 26 '12 at 23:27
@GSee -- Not at all! Thanks for that. I'm also glad Ben nudged me to undelete. — Josh O'Brien, Nov 26 '12 at 23:36
@user1854786 You're forming bad habits! `qqplot` is also a function in the `stats` package, which is loaded by default. As you've seen, creating functions with existing names can be very confusing; you should avoid it. — Gregor Thomas, Nov 27 '12 at 00:41

score 0 · Answer 2 · answered Nov 19 '20 at 19:02

Maybe you can write your own function:

xx <- matrix(c(3,7,4,8), 2, byrow = TRUE)
transp <- function(n){
    TM <- matrix(, nrow = ncol(n), ncol = nrow(n))
        for (i in 1 : nrow(TM)){
            for (j in 1 : ncol(TM)){
                TM[i, j] <- n[j, i]
            }
        }
    print(TM)
} 
transp(xx)

how to transpose a matrix in r if the usual `t( )` doesn't work?

2 Answers2

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