Message-ID: <1240739380.27308.3.camel@R1-Thux>
Date: 2009-04-26T09:49:40Z
From: Bernardo Rangel Tura
Subject: omit empty cells in crosstab?
In-Reply-To: <23224071.post@talk.nabble.com>
On Fri, 2009-04-24 at 13:12 -0700, sjaffe wrote:
> 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
Hi Steve
In your only 3 cells > 0
> d
b.1
b (0,1] (1,2] (2,3] (3,4] (4,5] (5,6] (6,7] (7,8] (8,9] (9,10]
(0,1] 0 0 0 0 0 0 0 0 0 0
(1,2] 0 1 0 0 0 0 0 0 0 0
(2,3] 0 0 1 0 0 0 0 0 0 0
(3,4] 0 0 0 0 0 0 0 0 0 0
(4,5] 0 0 0 0 0 0 0 0 0 0
(5,6] 0 0 0 0 0 0 0 0 0 0
(6,7] 0 0 0 0 0 0 0 0 0 0
(7,8] 0 0 0 0 0 0 0 0 0 0
(8,9] 0 0 0 0 0 0 0 0 0 0
(9,10] 0 0 0 0 0 0 0 0 0 1
If you desire use simple code to find only cell>0 use this
table(interaction(c,drop=T))
(1,2].(1,2] (2,3].(2,3] (9,10].(9,10]
1 1 1
--
Bernardo Rangel Tura, M.D,MPH,Ph.D
National Institute of Cardiology
Brazil