categorical data

Hello,

thats what I need, a list sorted first after year and then after
categorie. But I get an error message

df

      df     cate b    c
 [1,] "2006" "a1" "1"  "1"
 [2,] "2006" "a2" "2"  "2"
 [3,] "2005" "a1" "3"  "3"
 [4,] "2004" "a3" "1"  "1"
 [5,] "2004" "a2" "2"  "2"
 [6,] "2005" "a1" "3"  "3"
 [7,] "2003" "a2" "11" "11"
 [8,] "2003" "a1" "2"  "2"
 [9,] "2006" "a2" "3"  "3"

res<-aggregate( df[,c(3,4)], list(df$year,df$cate), sum)

Fehler in as.vector(x, mode) : Argument hat ung?ltigen 'mode'


(Error in as.vector(x,mode) :Argument has invalid mode)

I had tested the mode and receive "character". Can someone explain
what thats mean?

Christian



On Wed, 2006-08-09 at 18:07 +0200, Christian Oswald wrote:

Dear List,

I neeed a grouped list with two sort of categorical data. I have a
data .frame like this. 	year	cat.	b	c 1	2006	a1	125	212
2	2006	a2	256	212	 3	2005	a1	14	12 4	2004	a3	565	123
5	2004	a2	156	789	 6	2005	a1	1	456 7	2003	a2	786	123
8	2003	a1	421	569 9  	2002	a2	425	245

I need a list with the sum of b and c for every year and every cat
(a1, a2 or a3) in this year. I had used the tapply function to
build the sum for every year or every cat. How can I combine the
two grouping values?

Christian,

Is that what you want (using DF as your data.frame):

aggregate(DF[, c("b", "c")],

            by = list(Year = DF$year, Cat = DF$cat.),
            sum)
  Year Cat   b   c
1 2003  a1 421 569
2 2005  a1  15 468
3 2006  a1 125 212
4 2002  a2 425 245
5 2003  a2 786 123
6 2004  a2 156 789
7 2006  a2 256 212
8 2004  a3 565 123

You can also reorder the results by Year and Cat:

DF.result <- aggregate(DF[, c("b", "c")],

                         by = list(Year = DFyear, Cat = DF$cat.), sum)

DF.result[order(DF.result$Year, DF.result$Cat), ]

  Year Cat   b   c
4 2002  a2 425 245
1 2003  a1 421 569
5 2003  a2 786 123
6 2004  a2 156 789
8 2004  a3 565 123
2 2005  a1  15 468
3 2006  a1 125 212
7 2006  a2 256 212



Note that tapply() can only handle one 'X' vector at a time, whereas
aggregate can handle multiple 'X' columns in one call. For example:

tapply(DF$b, list(DF$year, DF$cat.), sum)

      a1  a2  a3
2002  NA 425  NA
2003 421 786  NA
2004  NA 156 565
2005  15  NA  NA
2006 125 256  NA

will give you the sum of 'b' for each combination of Year and Cat
within the 2d table, but I suspect this is not the output format you
want. You also get NA's in the cells where there was not the given
combination present in your data.

HTH,

Marc Schwartz