[R] converting to time series object : ts - package:stats

[Prof Brian Ripley]

On Mon, 26 Jun 2006, Sachin J wrote:

>  I am trying to convert a dataset (dataframe) into time series object 
> using ts function in stats package. My dataset is as follows:
>
>  >df
>  [1] 11.08 7.08  7.08  6.08  6.08  6.08  23.08 32.08 8.08  11.08 6.08  13.08 13.83 16.83 19.83 8.83  20.83 17.83
>  [19] 9.83  20.83 10.83 12.83 15.83 11.83

No data frame will print like that, so it seems that your description and 
printout do not match.

>  I converted this into time series object as follows
>
>  >tsdata <-  ts((df),frequency = 12, start = c(1999, 1))

>From the help page for ts:

     data: a numeric vector or matrix of the observed time-series
           values. A data frame will be coerced to a numeric matrix via
           'data.matrix'.

I suspect you have a single-column data frame with a factor column.
Look up what data.matrix does for factors.

>  The resulting time series is as follows:
>
>       Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
> 1999   2  15  15  14  14  14  12  13  16   2  14   5
> 2000   6   8  10  17  11   9  18  11   1   4   7   3
>
>  I am unable to understand why the values of df and tsdata does not 
> match. I looked at ts function and I couldn't find any data 
> transformation. Am I missing something here? Any pointers would be of 
> great help.
>
>  Thanks in advance.
>
>  Sachin

> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595