[R] count of factors

[Lucia Rueda]

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:
Apogonidae     Atherinidae       Blennidae      Blenniidae        Bothidae 
            216               1             406               2             
11 
     Carangidae Centracanthidae       Congridae         Gadidae        
Gobidae 
             25               4              21               2            
214 
     Haemulidae        Labridae       Mugilidae        Mullidae     
Muraenidae 
             25            6381              10             965             
45 
   Myliobatidae      Sciaenidae      Scombridae    Scorpaenidae     
Serranidae 
              2             159               1             512           
2127 
       Sparidae    Sphyraenidae    Synodontidae    Torpedinidae    
Trachinidae 
           6196               5               1               1              
1 
  Tripterygidae 
            135

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

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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