omit empty cells in crosstab?

I think the easiest way to deal with this problem is
to paste together the values, use table on those, and
then unpaste (strsplit) them back.  Using the 10 columns
with 10 levels example:
set.seed(25)
x = as.data.frame(replicate(10,sample(1:10,12,replace=TRUE)))
res = apply(x,1,paste,collapse=':')
tt1 = as.data.frame(table(res))
vals = strsplit(as.character(tt1$res),":")
answer = data.frame(do.call(rbind,vals),Freq=tt1$Freq)
answer
X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 Freq
1   10  8  3  3  5  9  9  6  5   2    1
2    1  1  3  6  2  7  7  7  1  10    1
3    2  6  6  8  9  7  2  8  6   3    1
4    2  7  1  2  2  4  3  4  3   2    1
5    3  5  2  3  6  3  4  7  6   7    1
6    4  1  9 10  2  9  6  1  4   1    1
7    4  2  5  8  2  2  1  4  6   3    1
8    4  8  4  8  2  9  2  3  4   1    1
9    5 10  3 10  1  2  1  9  7  10    1
10   7  5  9  6  6  5  2  5  7   2    1
11   7  6  4  4  8  3  8  8 10   6    1
12   9  2  6  2  8  7  5  4  2   1    1

                                        - Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu

small example:

a<-c(1.1, 2.1, 9.1)
b<-cut(a,0:10)
c<-data.frame(b,b)
d<-table(c)
dim(d)
##result: c(10, 10)

But only 9 of the 100 cells are non-zero.
If there were 10 columns, the table have 10 dimensions each of length 10, so
have 10^10 elements, too much even to fit in memory

Dieter Menne wrote:
sjaffe <sjaffe <at> riskspan.com> writes:

I have data with many factors, each taking many values. However, only
relatively few combinations appear in the data, ie have nonzero counts,
in
other words the resulting table is sparse. Say we have 10 factors each
with
10 levels. The result of table() would exceed the memory space (on a
32bit
machine). Is there any way to produce a table with empty cells omitted?
(without first producing the whole table and then removing rows.)
It would be easier if you had a reproducible base example, but I
suggest to create ONE new factor of the pasted levels using unique(),
and  creating a table of these.

Dieter

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and provide commented, minimal, self-contained, reproducible code.

omit empty cells in crosstab?

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