[R] sapply() with cat()

[Gabor Grothendieck]

Prof Brian Ripley <ripley <at> stats.ox.ac.uk> writes:

: 
: On Thu, 16 Sep 2004, Kevin Wang wrote:
: 
: > 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.
: 
: cat writes to connection (here stdout) and then returns NULL.  I think you 
: meant to use paste():
: 
: goo <- function(x)ifelse(x > 3.8, paste("\\textbf{", x, "}", sep = ""), x)
: 
: works.
: 


Also, if you convert your data frame to a matrix you won't need sapply:

   inter.mat <- as.matrix(inter.df)
   ifelse(inter.mat > 3.8, 
      paste("\\textbf{", inter.mat, "}", sep = ""), 
      inter.mat)