Re: [R] newbie help: simple operations in R

Simon Pickett Tue, 02 Jun 2009 04:23:56 -0700

The solution I provided should work

First off all give your data frame shorter and easier names e.g.


names(quatrro)<-c("x","y",etc)

since you want y(n)*x(n+1) an easy way to code this is to add on an "NA" to the 
start of x so everything shifts down a row and add an NA on the end of Y so 
that X and Y are the same length. look up the concatentae function ?c to 
understand this.

Data frame is not a problem. In that case its...

x<-c(NA,quattro$x)
y<-c(quattro$y,NA)
quattro$t<-quattro$x*quatrro$y

then

write.table(quattro,file="where you want the table to go.csv",sep="")

HTH, Si.



  ----- Original Message ----- 
  From: Carletto Rossi 
  To: Simon Pickett ; r-help@r-project.org 
  Sent: Tuesday, June 02, 2009 12:03 PM
  Subject: Re: [R] newbie help: simple operations in R


  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.






  2009/6/2 Simon Pickett <simon.pick...@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" <nuovo...@gmail.com>
    To: <r-help@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


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