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

[Alexander Shenkin]

Thanks, John.  Your solution gives me:

> ddply(my_df, .(a), summarize, mm = mean(dat), number = length(dat))
  a mm number
1 0 14      3
2 1 11      3

I'm looking for (and Ista found a way):

>>   a b c mean n
>> 1 1 * *   11 3
>> 2 * 1 *   14 3
>> 3 * * 1   12 3

thanks,
allie


On 3/20/2013 3:24 PM, John Kane wrote:
> Will this do?
> 
> library(plyr)
>   
>   ddply(my_df, .(a), summarize, mm = mean(dat), number = length(dat))
> 
> John Kane
> Kingston ON Canada
> 
> 
>> -----Original Message-----
>> From: ashenkin at ufl.edu
>> Sent: Wed, 20 Mar 2013 14:57:36 -0500
>> To: r-help at r-project.org
>> 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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> 
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