[R] summarize dataframe based on multiple cols, not their combinations

[arun]

Hi,
 lst1<- lapply(letters[1:3],function(i) {df1<-data.frame(my_df[i],my_df["dat"]); res<-ddply(df1,.(df1[[i]]),function(x) c("mean"=mean(x$dat),"n"=nrow(x)));names(res)[1]<-i;res<-res[res[,1]==1,]})

res1<-Reduce(function(...) merge(...,all=TRUE),lst1)
res1[is.na(res1)]<-"*"
 res1
#  mean n a b c
#1   11 3 1 * *
#2   12 3 * * 1
#3   14 3 * 1 *

A.K.



----- Original Message -----
From: Alexander Shenkin <ashenkin at ufl.edu>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, March 20, 2013 3:57 PM
Subject: [R] summarize dataframe based on multiple cols, not their combinations

Hi folks,

I'm trying to figure out how to get summarized data based on multiple
columns.  However, instead of giving summaries for every combination of
categorical columns, I want it for each value of each categorical column
regardless of the other columns.  I could do this with three different
commands, but i'm wondering if there's a more elegant way that I'm
missing.  Thanks!

allie

> my_df = data.frame(a = c(1,1,1,0,0,0), b=c(0,0,0,1,1,1),
c=c(1,0,1,0,1,0), dat=c(10,11,12,13,14,15))

> my_df
  a b c dat
1 1 0 1  10
2 1 0 0  11
3 1 0 1  12
4 0 1 0  13
5 0 1 1  14
6 0 1 0  15

> # not what I want
> ddply(my_df, .(a,b,c), function(x) c("mean"=mean(x$dat), "n"=nrow(x)))
  a b c mean n
1 0 1 0   14 2
2 0 1 1   14 1
3 1 0 0   11 1
4 1 0 1   11 2

What I want:
  a b c mean n
1 1 * *   11 3
2 * 1 *   14 3
3 * * 1   12 3

where "*" refers to any value of the other columns.

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