[R] beginner data.frame question

[John Fox]

Dear Kirk,

Actually, co2 isn't a data frame but rather a "ts" (timeseries) object. A
nice thing about R is that you can query and examine objects:

> class(co2)
[1] "ts"

> str(co2) # structure of object
 Time-Series [1:468] from 1959 to 1998: 315 316 316 318 318 ...

> unclass(co2)
  [1] 315.42 316.31 316.50 317.56 318.13 318.00 316.39 314 . . .
 [33] 314.83 315.16 315.94 316.85 317.78 318.40 319.53 320.42 . . .
 [65] 322.06 321.73 320.27 318.54 316.54 316.71 317.53 318.55 . . .
 [97] 322.17 322.34 322.88 324.25 324.83 323.93 322.38 320.76  . . .
. . .
[449] 365.45 365.01 363.70  . . . 360.83 362.49 364.34
attr(,"tsp")
[1] 1959.000 1997.917   12.000
>

(where . . . represents output that I've elided).

I hope this helps,
 John

------------------------------
John Fox, Professor
Department of Sociology
McMaster University
Hamilton, Ontario, Canada
web: socserv.mcmaster.ca/jfox


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
> Behalf Of Kirk Wythers
> Sent: December-23-08 6:30 PM
> To: r-help at r-project.org
> Subject: [R] beginner data.frame question
> 
> I need some help understanding how on of the example data sets is
> formatted in the basic R installation. If I load the Mona Loa CO2
> data, with the command:
> 
>  > data(co2)
> 
> I can view the data with:
> 
>  > co2
> 
> And the data are in the form of 11 rows labeled as years (1994-2004)
> and 12 columns labeled (Jan - Dec). This structure appears to be a
> dataframe, however, if I type the command
> 
>  > plot(co2)
> 
> I get a time series with CO2 on the x axis and time on the y. Also,
> 
>  > summary(co2) gives a single Min, Median, Max.
> 
> The reason for my confusion is that I created another "similar
> looking" data set with read.table. In that case, the data looks to be
> in same format (rows as years, and columns as months). However, the
> command
> 
>  > summary(test.data)
> 
> gives a summary for each month. Completely different behavior.
> 
> If use the data.frame command:
> 
>  > data.frame(co2)
> 
> I get a single column of CO2 data, while the data.frame command on my
> test.data data, keeps it's year-row, column-month format.
> 
> Can anyone help me understand the differences in how these data sets
> are formatted?
> 
> Thanks in advance.
> 
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