[R] Odp: count of factors

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 19.01.2011 09:51:43:

> 
> Hello everyone,
> 
> I have a data set like this:
> 
> > head( fish_transect)
>   ID_TRANSECT ID_PROJECT   DE_ZONE DE_LOCALITY DE_SECTOR MES
> 1          42         MB Tarragona    Creixell Control I   9
> 2          42         MB Tarragona    Creixell Control I   9
> 3          42         MB Tarragona    Creixell Control I   9
> 4          42         MB Tarragona    Creixell Control I   9
> 5          42         MB Tarragona    Creixell Control I   9
> 6          42         MB Tarragona    Creixell Control I   9
>                ID_SPECIES         WEIGHT  SIZE   N    FAMILIA
> 1 Spondyliosoma cantharus    15.64     10     1    Sparidae
> 2  Symphodus melanocercus  11.21     10      1   Labridae
> 3       Diplodus vulgaris         30.20     10      2   Sparidae
> 4       Diplodus vulgaris         52.24     12      2   Sparidae
> 5         Diplodus sargus        221.41    14     5    Sparidae
> 6      Diplodus annularis         3.47       6      1    Sparidae
> 
> The table function of the column FAMILIA gives:

<snip>

> 
> I want to add a new column "familia2" where those families with low 
number
> of individuals are listed as "other", that is, for these families
> Atherinidae      Blenniidae        Bothidae      Carangidae 
Centracanthidae 
>               1               2              11              25  
> 4 
>       Congridae         Gadidae      Haemulidae       Mugilidae 
> Muraenidae 
>              21               2              25              10  
> 45 
>    Myliobatidae      Scombridae    Sphyraenidae    Synodontidae 
> Torpedinidae 
>               2               1               5               1  
> 1 
>     Trachinidae 
>               1
> 

Use levels
make new column 
fish_transect$familia2 <- fish_transect$familia

change levels
levels(fish_transect$familia2)[which(table(fish_transect$familia2)<46)]<-"other"

You can use any threshold number.

Regards
Petr

BTW you need to have familia as factor not as character variable.



> I want them in column "familia2" to be named "others"
> 
> I've been trying to do a loop telling R to write "others" when the sum 
of
> FAMILIA was less than 50, but it didn't work because FAMILIA is a 
factor,
> and there isn't a "count" function (or I didn't find it). I also tried 
other
> options like the "match" function, "level" function, etc. I know I can 
do it
> manually typing by myself the names of the 16 families but I want to 
learn a
> way to do where I don't need to type the names.
> 
> Thanks in advance!
> 
> Lucia
> 
> 
> -- 
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> tp3224791p3224791.html
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