How to list the all products' information of the latest month?

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Hi,

I have data frame like this:

Product     Price    Year_Month  PE
A                 100        201012         -2
A                 98           201101        -3
A                 97           201102        -2.5
B                 110         201101        -1
B                 100         201102        -2
B                  90          201103        -4


How can I achieve the following result using R:
Product     Price    Year_Month  PE
A                 97           201102        -2.5
B                  90          201103        -4

Another option is to use aggregate like this

aggregate(x, by=list(x$Product), FUN=function(z) tail(z,1))[,-1]

or

aggregate(. ~ Product, data=x, FUN=function(z) tail(z,1))


Berend

dat1<- read.table(text="
Product??? Price??? Year_Month? PE
A??????????????? 100??????? 201012??????? -2
A??????????????? 98????????? 201101??????? -3
A??????????????? 97????????? 201102??????? -2.5
B??????????????? 110??????? 201101??????? -1
B??????????????? 100??????? 201102??????? -2
B????????????????? 90????????? 201103??????? -4
",sep="",header=TRUE,stringsAsFactors=FALSE)
dat1[as.logical(with(dat1,ave(Year_Month,Product,FUN=function(x) x==max(x)))),]
#? Product Price Year_Month?? PE
#3?????? A??? 97???? 201102 -2.5
#6?????? B??? 90???? 201103 -4.0
A.K.




----- Original Message -----
From: Tammy Ma <metal_licaling at live.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Friday, March 15, 2013 5:56 AM
Subject: [R] How to list the all products' information of the latest month?

Hi,

I have data frame like this:

Product? ?  Price? ? Year_Month? PE
A? ? ? ? ? ? ? ?  100? ? ? ? 201012? ? ? ?  -2
A? ? ? ? ? ? ? ?  98? ? ? ? ?  201101? ? ? ? -3
A? ? ? ? ? ? ? ?  97? ? ? ? ?  201102? ? ? ? -2.5
B? ? ? ? ? ? ? ?  110? ? ? ?  201101? ? ? ? -1
B? ? ? ? ? ? ? ?  100? ? ? ?  201102? ? ? ? -2
B? ? ? ? ? ? ? ? ? 90? ? ? ? ? 201103? ? ? ? -4


How can I achieve the following result using R:
Product? ?  Price? ? Year_Month? PE
A? ? ? ? ? ? ? ?  97? ? ? ? ?  201102? ? ? ? -2.5
B? ? ? ? ? ? ? ? ? 90? ? ? ? ? 201103? ? ? ? -4

in other words, list the all products' information of the latest month?

Thanks for your help.

Kind regards,
Lingyi




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