[R] the format of the result

[Marc Schwartz (via MN)]

On Fri, 2005-07-01 at 19:40 +0800, ronggui wrote:
> I write a function to get the frequency and prop of a variable.
> 
> freq<-function(x,digits=3)
> {naa<-is.na(x)
> nas<-sum(naa)
> if (any(naa))
> x<-x[!naa]
> n<-length(x)
> ta<-table(x)
> prop<-prop.table(ta)*100
> res<-rbind(ta,prop)
> rownames(res)<-c("Freq","Prop")
> cat("Missing value(s) are",nas,".\n")
> cat("Valid case(s) are",n,".\n")
> cat("Total case(s) are",(n+nas),".\n\n")
> print(res,digits=(digits+2))
> cat("\n")
> }
> 
> > freq(sample(letters[1:3],48,T),2)
> Missing value(s) are 0 .
> Valid case(s) are 48 .
> Total case(s) are 48 .
> 
>          a     b     c
> Freq 11.00 20.00 17.00
> Prop 22.92 41.67 35.42
> 
> and i want the result to be like
>          a      b     c
> Freq 11.00  20.00  17.00
> Prop 22.92% 41.67% 35.42%
> 
> how should i change my function to get what i want?


Here is a modification of the function that I think should work. Note
that part of the output formatting process has to take into account the
a priori unknowns involving your 'digits' argument, the lengths of the
dimnames resulting from the table and the lengths of the frequency
counts in the table. Thus, a fair amount of the code is establishing the
'width' argument, which is then used in formatC() so that the output can
be column aligned properly.

Note that by default, table() will exclude "NA", so you do not need to
subset 'x' before using table().

Also, note that I change "Prop" to "Pct".


freq <- function(x, digits = 3)
{
  n <- length(x)
  missing <- sum(is.na(x))
  ta <- table(x)
  pct <- prop.table(ta) * 100

  width <- max(nchar(unlist(dimnames(ta))) + 1,
               nchar(ta) + digits + 1,
               5 + digits)
  
  Vals <- paste(formatC(unlist(dimnames(ta)), format = "s",
                        width = width),
                collapse = "  ")

  Freq <- paste(formatC(ta, format = "f", digits = digits,
                        width = width),
                collapse = "  ")

  Pct <- paste(formatC(pct, format = "f", digits = digits,
                       width = width),
               "%", sep = "", collapse = " ")

  cat("Missing value(s) are", missing, ".\n")
  cat("Valid case(s) are", n - missing,".\n")
  cat("Total case(s) are", n, ".\n\n")

  cat("    ", Vals, "\n")
  cat("Freq", Freq, "\n")
  cat("Pct ", Pct, "\n")
  cat("\n")
}


Thus:


> freq(sample(letters[1:3], 48, TRUE), 2)
Missing value(s) are 0 .
Valid case(s) are 48 .
Total case(s) are 48 .

           a        b        c 
Freq   28.00     8.00    12.00 
Pct    58.33%   16.67%   25.00% 


> freq(sample(c(letters[1:3], NA), 1000, TRUE), 2)
Missing value(s) are 257 .
Valid case(s) are 743 .
Total case(s) are 1000 .

           a        b        c 
Freq  250.00   218.00   275.00 
Pct    33.65%   29.34%   37.01% 


> freq(iris$Species)
Missing value(s) are 0 .
Valid case(s) are 150 .
Total case(s) are 150 .

          setosa   versicolor    virginica 
Freq      50.000       50.000       50.000 
Pct       33.333%      33.333%      33.333% 


> freq(iris$Species, 0)
Missing value(s) are 0 .
Valid case(s) are 150 .
Total case(s) are 150 .

          setosa   versicolor    virginica 
Freq          50           50           50 
Pct           33%          33%          33% 


HTH,

Marc Schwartz