[R] Problem with cat() == A related question

[William Dunlap]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Peng, C
> Sent: Thursday, September 16, 2010 5:39 AM
> To: r-help at r-project.org
> Subject: Re: [R] Problem with cat() == A related question
> 
> 
> The question is wehter cat() can print out a matrix as it is. 
> For example,
> Let's assume that we have matrices A, B, D(= A+B), if it is 
> possible that
> cat("\n", A, "+",B,"=", D, < some control arguments >, "\n")
> prints out
> 
>   matrix A +  matrix B  = matrix D
> 
> where matrices A, B, D (= A+B) should be in the form of their actual
> matrices.

cat() will not do that.  I use a function, SideBySide(x,y)
to print two objects next to each other.  It does it by
capturing the printed output of each as character vectors,
then cbinding them together into a 2 column character matrix
which the standard print routine will print nicely.
Typical usage is
  > A<-matrix(1:12,nrow=3)
  > B<-matrix(100,nrow=3,ncol=4)
  > sideBySide(A,A+B)
   A                        A + B                   
        [,1] [,2] [,3] [,4]      [,1] [,2] [,3] [,4]
   [1,]    1    4    7   10 [1,]  101  104  107  110
   [2,]    2    5    8   11 [2,]  102  105  108  111
   [3,]    3    6    9   12 [3,]  103  106  109  112

Perhaps you can adapt it to your needs by letting it
take more than two arguments and adding some separators.
  sideBySide <- function (a, b, argNames) {
    oldWidth <- options(width = getOption("width")/2 - 4)
    on.exit(options(oldWidth))
    if (missing(argNames)) {
        argNames <- c(deparse(substitute(a))[1],
deparse(substitute(b))[1])
    }
    pa <- capture.output(print(a))
    pb <- capture.output(print(b))
    nlines <- max(length(pa), length(pb))
    length(pa) <- nlines
    length(pb) <- nlines
    pb[is.na(pb)] <- ""
    pa[is.na(pa)] <- ""
    retval <- cbind(pa, pb, deparse.level = 0)
    dimnames(retval) <- list(rep("", nrow(retval)), argNames)
    noquote(retval)
  }

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 

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