R help - Jun 2009 - newbie help: simple operations in R

Hi, i' d like to use R for simple calculations. I show you an examples to
make clear my help request

I' ve a file .csv like this (my real file is composed by 10.000 lines and 8
columns)

x y
3 4
1 7

I' ve imported in R correctly. Now i want create a new variable named
"t"
and t is defined throught this relation:

t = 4 (second element on x column) * 4 (first element on y column)

in what way can i calculate t and print its value on an external file or,
better, append t values as a column on my original csv???

Thanks

Emanuele

	[[alternative HTML version deleted]]

you could use a loop but maybe easier would be
x<-c(NA,x)
y<-c(y,NA)
t<-x*y

use write.table() to write the table to your hard drive

e.g.

write.table(t, file="C:/Documents and Settings/simonp/My Documents/RELU/GIS
data/Land Cover Map working/squares plus adjoining parcels/Scotland/scotland 
adj squares.csv", sep = ",",row.names = F)

HTH, Si.

----- Original Message ----- 
From: "Carletto Rossi" <nuovodna at gmail.com>
To: <r-help at r-project.org>
Sent: Tuesday, June 02, 2009 11:22 AM
Subject: [R] newbie help: simple operations in R

> Hi, i' d like to use R for simple calculations. I show you an examples
to
> make clear my help request
>
> I' ve a file .csv like this (my real file is composed by 10.000 lines
and
> 8
> columns)
>
> x y
> 3 4
> 1 7
>
> I' ve imported in R correctly. Now i want create a new variable named
"t"
> and t is defined throught this relation:
>
> t = 4 (second element on x column) * 4 (first element on y column)
>
> in what way can i calculate t and print its value on an external file or,
> better, append t values as a column on my original csv???
>
> Thanks
>
> Emanuele
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Hi

r-help-bounces at r-project.org napsal dne 02.06.2009 12:22:49:
> Hi, i' d like to use R for simple calculations. I show you an examples 
to
> make clear my help request
> 
> I' ve a file .csv like this (my real file is composed by 10.000 lines 
and 8
> columns)
> 
> x y
> 3 4
> 1 7
> 
> I' ve imported in R correctly. Now i want create a new variable named 
"t"
> and t is defined throught this relation:
> 
> t = 4 (second element on x column) * 4 (first element on y column)
> 
> in what way can i calculate t and print its value on an external file 
or,
> better, append t values as a column on my original csv???
It is rather difficult to evaluate what you really want to do. You say you 
have 10000 rows and 8 columns and your small example has only 2 columns 
and 2 rows.  Do you want to use third and subsequent row, or third and 
further columns? If yes how?

If you want to multiply second with first and third with second and ... 
than

DF <- data.frame(x=c(5,3,7), y=c(1,4,2))

drop the first item from x and last item from y and multiply

DF[-1,1]*DF[-3,2]

Regards
Petr
> 
> Thanks
> 
> Emanuele
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.