[R] How to do a backward calculation for each record in a dataset

[arun]

Hi,
I am  not sure I understand it correctly.

dat1<-read.table(text="
customer.name    product    cost
John    Toothpaste    30
Mike    Toothpaste    45
Peter    Toothpaste    40
",sep="",header=TRUE,stringsAsFactors=FALSE)
 dat1$no.of.orders<-  sqrt((dat1$cost-3.40)/1.20)
 dat1
#  customer.name    product cost no.of.orders
#1          John Toothpaste   30     4.708149
#2          Mike Toothpaste   45     5.887841
#3         Peter Toothpaste   40     5.522681
A.K.





----- Original Message -----
From: Prakasit Singkateera <asltjoey.rsoft at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Sunday, February 17, 2013 8:10 AM
Subject: [R] How to do a backward calculation for each record in a dataset

Hi Experts,

I have a dataset of 3 columns:

customer.name     product     cost
John     Toothpaste     30
Mike     Toothpaste     45
Peter     Toothpaste     40

And I have a function of cost whereby

cost = 3.40 + (1.20 * no.of.orders^2)

I want to do a backward calculation for each records (each customer) to
find his no.of.orders and create a new column named "no.of.orders" in that
dataset but I don't know how to do.

Please help me.

Thank you everyone,
Prakasit

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