[R] Restructuring Hadley CET data

[hadley wickham]

Hi Ted,

melt(df, id=c("year","DoM"))
should get you started.

Hadley

On 4/27/07, Ted Harding <ted.harding at nessie.mcc.ac.uk> wrote:
> Hi Folks,
> I have a nasty data restructuring problem!
>
> I can think of one or two really clumsy ways of doing it
> with 'for' loops and the like, but I can't think of a
> *neat* way of doing it in R.
>
> The data are the Hadley Centre "Central England Temperature"
> series, daily from 01/01/1772 to 31/03/2007, and can be
> viewed/downloaded at
>
>   http://hadobs.metoffice.com/hadcet/cetdl1772on.dat
>
> and the structure is as follows:
>
> Year DoM Jan  Feb Mar  Apr May  Jun Jul Aug  Sep Oct  Nov Dec
> -------------------------------------------------------------
> 1772  1   32  -15  18   25  87  128 187 177  105 111   78 112
> 1772  2   20    7  28   38  77  138 154 158  143 150   85  62
> 1772  3   27   15  36   33  84  170 139 153  113 124   83  60
> 1772  4   27  -25  61   58  96   90 151 160  173 114   60  47
> 1772  5   15   -5  68   69 133  146 179 170  173 116   83  50
> 1772  6   22  -45  51   77 113  105 175 198  160 134  134  42
> .................................
> .................................
> 1772 27    0   46  66   74  77  198 156 144   76 104   45   5
> 1772 28   15   77  86   64 116  167 151 155   66  84   60  10
> 1772 29  -33   56  83   50 113  131 170 182  135 140   63  12
> 1772 30  -10 -999  66   77 121  122 179 163  143 143   55  15
> 1772 31   -8 -999  46 -999 108 -999 168 144 -999 145 -999  22
> 1773  1   20    0  79   13  93  174 104 151  171 131   68  55
> 1773  2   10   17  71   25  65  109 128 184  164  91   34  75
> 1773  3    5  -28  94   70  41   79 135 192  149 101   78  85
> 1773  4    5  -23  99  107  49  107 144 173  144  98   86  83
> 1773  5  -28  -30  76   65  83  128 144 182  116  98   66  38
> .................................
>
> "DoM" is Day of Month, 1-31 for each month ("short" months
> get entries -999 on missing days).
>
> So each year is a block of 31 lines and 14 columns, pf
> which the last 12 are Temperature (in 10ths of a degreeC),
> each column a month, running down each column for the
> 31 days of the month in that year.
>
> What I want to do is convert this into a 4-column format:
>
>   Year, Month, DoM, Temp
>
> with a separate row for each consecutive day from 01/01/1772
> to 31/02/2007, and omitting days which have a "-999" entry
> (OK I still have to check that "-999" is only used for DoMs
> which don't exist, and don't also indicate that a Temperature
> may be missing for some other reason; but I believe the series
> to be complete).
>
> What it boils down to is stacking the 12 31-day Temperature
> columns on top of each other in each year, filling in the
> Year, Month, DoM, and stacking the results for consecutive
> years on top of each other (after which one can strike out
> the "-999"s). Hence, really clunky for-loops!
>
> Any really *neat* ideas for this?
>
> With thanks,
> Ted.
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 27-Apr-07                                       Time: 22:24:51
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