[R] Basic loop programming

[arun]

HI,

If you have more than one observation per month, you could do this:
dat1<-read.table(text="
Year Month    Sales    Customer
2011    Jan    150     35
2011    Jan    125     40
2011    Feb    130     45
2011    Feb    135     25
2012    Jan    100     25
2012    Jan    150     35
2012    Feb    118     45 
2012    Feb    120     30
2012    Mar    130     43
2012    Mar    125     35
",sep="",header=TRUE,stringsAsFactors=FALSE)
res<-aggregate(.~Year+Month,data=dat1,mean)
 within(res,{Avrev<-Sales/Customer})
#  Year Month Sales Customer    Avrev
#1 2011   Feb 132.5     35.0 3.785714
#2 2012   Feb 119.0     37.5 3.173333
#3 2011   Jan 137.5     37.5 3.666667
#4 2012   Jan 125.0     30.0 4.166667
#5 2012   Mar 127.5     39.0 3.269231


A.K.



----- Original Message -----
From: Paolo Donatelli <donatellipaolo at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, January 9, 2013 11:02 AM
Subject: [R] Basic loop programming

Hi all,

newbie question: I am trying to set up a very simple loop without succeeding.

Let's say I have monthly observation of two variables for a year
- Sales_2012_01, Sales_2012_02, Sales_2012_03, ....      (total sales
for jan 2012,feb 2012, etc.)
- Customers_2012_01, Customers_2012_02, ....  (total number of
customers for jan 2012, etc.)

and I want to create new monthly variables in order to compute
revenues per customers:

Av_revenue_2012_01 = Sales_2012_01 / Customers_2012_01
Av_revenue_2012_02 = Sales_2012_02 / Customers_2012_02
...

how can I proceed?


In other programming language I used just to write something like
for (i in list("01","02, ..., "12") {
Av_revenue_2012_'i' = Sales_2012_'i' / Customers_2012_'i'
}

but in R it seems not to work like that. Further, and correct me if I
am wrong, I cannot use simple (i in 1:12) since I have a 0 digit in
front of the single-digit months.

thanks in advance for your help

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