[R] newbie help: simple operations in R

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 02.06.2009 13:03:39:

> I' ve tried your suggestions but the results are wrong.I don't
> understand...i explain my request in a new way.
> I have this table named data-4-bk.csv
> 
> "Y/h","u/U_b","v/U_b","uu/U_b^2","vv/U_b^2","uv/U_b^2","k/U_b^2"
> 
0.16067E-02,-0.11652E-01,0.30712E-04,0.11377E-02,0.37886E-06,-0.12657E-05,0.13570E-02
> 
0.48616E-02,-0.28583E-01,-0.10085E-03,0.72322E-02,0.44299E-04,-0.17874E-04,0.78991E-02
> 
0.82005E-02,-0.40079E-01,-0.25124E-03,0.14272E-01,0.23333E-03,-0.75078E-04,0.15054E-01
> 
0.11625E-01,-0.47481E-01,-0.50081E-03,0.19783E-01,0.60134E-03,-0.17623E-03,0.20764E-01
> 
0.15139E-01,-0.52047E-01,-0.78504E-03,0.23607E-01,0.11297E-02,-0.31123E-03,0.25042E-01
> 
0.18743E-01,-0.54658E-01,-0.11273E-02,0.26189E-01,0.17884E-02,-0.46941E-03,0.28287E-01
> 
0.22439E-01,-0.55902E-01,-0.15016E-02,0.27935E-01,0.25450E-02,-0.64447E-03,0.30825E-01
> 
0.26231E-01,-0.56181E-01,-0.19149E-02,0.29136E-01,0.33728E-02,-0.83204E-03,0.32881E-01
> 
0.30121E-01,-0.55777E-01,-0.23570E-02,0.29974E-01,0.42480E-02,-0.10299E-02,0.34591E-01
> 
0.34111E-01,-0.54897E-01,-0.28303E-02,0.30577E-01,0.51528E-02,-0.12376E-02,0.36045E-01
> 
0.38204E-01,-0.53696E-01,-0.33293E-02,0.31034E-01,0.60717E-02,-0.14533E-02,0.37305E-01
> 
0.42403E-01,-0.52267E-01,-0.38533E-02,0.31403E-01,0.69931E-02,-0.16763E-02,0.38415E-01
> 
0.46709E-01,-0.50663E-01,-0.43996E-02,0.31712E-01,0.79083E-02,-0.19064E-02,0.39403E-01
> 
> I give these R commands to import the file
> 
> quattro <- read.csv('data-4-bk.csv', header=TRUE)
> attach(quattro)
> names(quattro)
> 
> Then i'd like to calculate the new variable "t" defined as:
> 
> First element of u/U_b column * Second element of Y/h column
> Second element of u/U_b column * Third element of Y/h column
> etc.. etc..
> 
> Now i' d like to print the values of t as a new column on the original
> data-4-bk.csv
> 
> Thanks and sorry for my newbie request.

My previous solution will work but you need to drop last element from u/U 
column.

so do not attach and use

quattro[-nrow(quattro),"u/U"] * quattro[-1,"Y/h"]

then you will get one item less and you need to decide if NA value will be 
at the beginning or at the end.

Regards
Petr




> 
> 
> 
> 
> 
> 2009/6/2 Simon Pickett <simon.pickett at bto.org>
> 
> > 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.
> >>
> >>
> >
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.