[R] Calculate of data frame

[Zhang, Fan]

Hello,
 
I have a dataframe which I read from a file:
 
df - readtable(myFile);
 
The dataframe has 4 columns: model, count, value and date where
model and date are made of charactors and count and value are
numbers. An example is like:
modelcountvaluedate
A420.87/1/2005
A310.27/2/2005
B714.27/1/2005
B16.2  7/2/2005
A2117/1/2005
B965.2 7/2/2005
 
Now I want to get the total count and value for each model/date pair,
like
modelcountvaluedate
A631.87/1/2005
A310.27/2/2005
B714.27/1/2005
B1067.4  7/2/2005
 
Anyone can tell me how to do this?
 
Thanks.
 
Fan

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Re: [R] Calculate of data frame

[Zhang, Fan]

Thanks for your answer, Peter. Now I have a new data frame which is sorted by 
(model,date) pair. Since the sorting is done to charactors, I have 7/1/2005 
followed by 7/10/2005 instead of 7/2/2005. How can I do the aggregation and at 
the same time, make the result sorted the way I want (i.e, 7/1/2005 followd by 
7/2/2005)? 

Thanks,

Fan
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Dalgaard
Sent: Thursday, July 14, 2005 1:29 PM
To: Zhang, Fan
Cc: r-help@stat.math.ethz.ch
Subject: Re: [R] Calculate of data frame

Zhang, Fan [EMAIL PROTECTED] writes:

 Now I want to get the total count and value for each model/date pair, 
 like
 modelcountvaluedate
 A631.87/1/2005
 A310.27/2/2005
 B714.27/1/2005
 B1067.4  7/2/2005
  
 Anyone can tell me how to do this?

 aggregate(df[,c(count,value)],df[,c(date,model)],sum)
  date model count value
1 7/1/2005 A 6  31.8
2 7/2/2005 A 3  10.2
3 7/1/2005 B 7  14.2
4 7/2/2005 B10  71.4


-- 
   O__   Peter Dalgaard Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark  Ph:  (+45) 35327918
~~ - ([EMAIL PROTECTED])  FAX: (+45) 35327907

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