[R] sapply() with cat()

[Kevin Wang]

Hi,

Suppose I've got a data frame:
   > inter.df
       V1  V2  V3  V4  V5  V6  V7  V8  V9 V10 V11 V12
   1  3.3  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA
   2  0.0 0.1  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA
   3  1.0 0.9 0.2  NA  NA  NA  NA  NA  NA  NA  NA  NA
   4  1.6 0.0 2.9 0.7  NA  NA  NA  NA  NA  NA  NA  NA
   5  0.0 0.1 2.9 0.1 0.1  NA  NA  NA  NA  NA  NA  NA
   6  2.4 1.0 0.6 0.4 1.9 0.1  NA  NA  NA  NA  NA  NA
   7  2.8 1.4 1.2 7.5 0.0 0.0 4.2  NA  NA  NA  NA  NA
   8  0.3 3.1 0.8 3.7 5.7 0.0 0.8 0.0  NA  NA  NA  NA
   9  0.1 2.9 0.3 1.3 0.2 0.2 0.5 1.4 0.9  NA  NA  NA
   10 0.8 2.6 0.0 0.0 0.1 4.1 0.8 4.3 0.6 2.2  NA  NA
   11 0.0 4.0 0.0 0.3 0.5 0.9 0.0 1.5 0.2 0.7 0.8  NA
   12 0.6 0.8 0.3 0.0 0.2 1.2 0.0 0.8 1.5 0.9 0.4   0
   >
   > foo <- function(x) {
   +   ifelse(x > 3.8, NA, x)
   + }
   > sapply(inter.df, foo)
          V1  V2  V3  V4  V5  V6  V7  V8  V9 V10 V11 V12
    [1,] 3.3  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA
    [2,] 0.0 0.1  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA
    [3,] 1.0 0.9 0.2  NA  NA  NA  NA  NA  NA  NA  NA  NA
    [4,] 1.6 0.0 2.9 0.7  NA  NA  NA  NA  NA  NA  NA  NA
    [5,] 0.0 0.1 2.9 0.1 0.1  NA  NA  NA  NA  NA  NA  NA
    [6,] 2.4 1.0 0.6 0.4 1.9 0.1  NA  NA  NA  NA  NA  NA
    [7,] 2.8 1.4 1.2  NA 0.0 0.0  NA  NA  NA  NA  NA  NA
    [8,] 0.3 3.1 0.8 3.7  NA 0.0 0.8 0.0  NA  NA  NA  NA
    [9,] 0.1 2.9 0.3 1.3 0.2 0.2 0.5 1.4 0.9  NA  NA  NA
   [10,] 0.8 2.6 0.0 0.0 0.1  NA 0.8  NA 0.6 2.2  NA  NA
   [11,] 0.0  NA 0.0 0.3 0.5 0.9 0.0 1.5 0.2 0.7 0.8  NA
   [12,] 0.6 0.8 0.3 0.0 0.2 1.2 0.0 0.8 1.5 0.9 0.4   0

Up to here, sapply() does what I want, replacing values that are greater 
than 3.8 to NA, as per my foo() function.  But...

   > goo <- function(x) {
   +   ifelse(x > 3.8, cat("\\textbf{", x, "}", sep = ""), x)
   + }
   > sapply(inter.df, goo)
   \textbf{NA0.10.900.111.43.12.92.640.8}Error in "[<-"(`*tmp*`, test, 
value = rep(yes, length.out = length(ans))[test]) :
           incompatible types

If instead whenever I get a value that's greater than 3.8 I want to 
change it what goo() does, e.g. the value 4.0 should become:
   \textbf{4.0}
but I got the above error.

What I'm intending is to then pass the inter.df (with the \textbf{} 
markups) into xtable() so the values will be bolded in the resulting 
LaTeX table (as so far, I cannot see how I can achieve bolding only 
certain numbers with xtable() alone).

Any suggestions will be welcome!

Kevin

-- 
Ko-Kang Kevin Wang
PhD Student
Centre for Mathematics and its Applications
Building 27, Room 1004
Mathematical Sciences Institute (MSI)
Australian National University
Canberra, ACT 0200
Australia

Homepage: http://wwwmaths.anu.edu.au/~wangk/
Ph (W): +61-2-6125-2431
Ph (H): +61-2-6125-7407
Ph (M): +61-40-451-8301