[R] newbie: data frame to vector

[Ko-Kang Kevin Wang]

Hi,

----- Original Message -----
From: "Eric Peterson" <peterson at heritage.nv.gov>
To: <r-help at stat.math.ethz.ch>
Sent: Wednesday, January 22, 2003 10:47 AM
Subject: [R] newbie: data frame to vector


> Sorry, but I'm very new to R.  I'm trying to figure out how to convert a
> column from a data frame to a vector.  More specifically, I have read in a
> comma separated value table which contains a number of variables in
columns,
> plots in rows...
>
> t <- read.table("G:/R/table1.txt", sep=",", header=TRUE)
>
> the data comes in just fine.  Now I want to do an XY plot of 2 variables
and
> will be doing some statistical analyses on them.  But
>
> plot(t["Var1"], t["Var2"])


I'm assuming your data frame, t, looks like:
  Var1  Var2  Var3
        1        2        3
        4        5        6
        7        8        9

Then there are (at least) two ways.  The first is type:
  attach(t)
right after your
  > t <- read.table("G:/R/table1.txt", sep=",", header=TRUE)
this will allow you to use the column names directly, i.e. you can do:
  plot(Var1, Var2)

If you do not attach it, you can still achieve your goal.  Remember that the
data frame is two dimensional, to subset a two dimensional object you need a
comma, i.e
  t[1, ]  # give you row 1
  t[, 1]  # give you column 1
  t[1, 1] # give you the first value in row 1, column 1

So to do what you want you need:
  plot(t[, 1], t[, 2])  # Plot Column 1 and 2

Hope this helps,

Kevin Wang


------------------------------------------------
Ko-Kang Kevin Wang
Master of Science (MSc) Student
Department of Statistics
University of Auckland
New Zealand
www.stat.auckland.ac.nz/~kwan022