r print frequencies above a value

Question

How do I print the significant frequencies in a table, with row / column names?

with(mtcars,table(cyl,carb))

   carb
cyl 1 2 3 4 6 8
  4 5 6 0 0 0 0
  6 2 0 0 4 1 0
  8 0 4 3 6 0 1

I'd like to see the rows and columns for frequencies 5 and above

   carb
cyl 1 2 4
  4 5 6 0
  8 0 4 6

Or, any suggestions on how to see the significant data in a frequency table with 100 rows and 200 columns.

Can the following be printed?

cyl  carb  count
4     1      5
4     2      5
8     4      6

Answer 1

You could try:

tbl <- with(mtcars, table(cyl, carb))
dat1 <- subset(as.data.frame(with(mtcars,table(cyl,carb))), Freq>=5) 
tbl2 <- xtabs(Freq~., droplevels(dat1))
indx <- match(outer(rownames(tbl2), colnames(tbl2), FUN=paste0),outer(rownames(tbl), colnames(tbl), FUN=paste0))

 tbl2[] <- tbl[indx]
 tbl2
 #  carb
#cyl  1 2 4
#   4 5 6 0
#   8 0 4 6

Or

  indx <- tbl>=5
  tbl[!!rowSums(indx), !!colSums(indx)]
    carb
 #cyl 1 2 4
 #  4 5 6 0
 #  8 0 4 6

Answer 2

For your first question, you can use the arr.ind argument of which to get the rows and columns that you wish to select:

x <- with(mtcars,table(cyl,carb))
inds <- which(x>=5,arr.ind=TRUE)

x[unique(inds[,"row"]),unique(inds[,"col"])]
   carb
cyl 1 2 4
  4 5 6 0
  8 0 4 6

The second question is easier, just coerce to data.frame and subset :

subset(as.data.frame(x),Freq>=5)
   cyl carb Freq
1    4    1    5
4    4    2    6
12   8    4    6