[R] categorical variables

[Clément Calenge]

At 14:49 14/04/2003 +0100, Luis Silva wrote:
>Dear helpers
>
>I constructed a data frame with this structure
>
> > str(dados1)
>`data.frame':   485 obs. of  16 variables:
>  $ Emissor         : int  1 1 1 1 1 1 1 1 1 1 ...
>  $ Marisca.Rio     : int  1 1 1 1 1 1 1 1 1 1 ...
>  $ Período         : int  1 1 1 1 1 1 1 1 1 1 ...
>  $ Reproducao      : int  3 3 3 3 3 3 3 3 3 3 ...
>  $ Estacao         : int  2 2 2 2 2 2 2 2 2 2 ...
>  $ X30cm           : int  1 1 1 1 1 1 1 1 1 1 ...
>  $ Dir.mov         : int  0 0 0 0 0 0 0 0 0 0 ...
>  $ Temp.media      : num  12.0 11.3 12.1 12.3 12.4 ...
>  $ Temp.amplitude  : num   1.167 -0.750  0.875  0.125 ...
>  $ Vel.media       : num  0.479 0.514 0.517 0.445 0.468 ...
>  $ Vel.amplitude   : num  -0.04865  0.03417  0.00312 0.02364 ...
>  $ Caudal.medio    : num  0.570 0.585 0.589 0.485 0.501 ...
>  $ Caudal.amplitude: num  -0.04323  0.01449  0.00405 0.01617 ...
>  $ Prof.media      : num  36.1 34.6 34.1 32.9 32.1 ...
>  $ Prof.amplitude  : num   0.458 -1.500 -0.500 -1.250 -0.750 ...
>  $ Movimento       : num  0 0 0 0 0 0 0 0 0 0 ...
>
>My problem is that the first 7 variables are in fact
>categorical, some of them of the type Present/Absent. R is
>taking them as integer but I want categorical. How can I solve
>this problem? I searched data.frame help but I didn't found any
>parameter to set some variables to categorical



see ?factor:

for (i in 1:7) dados1[,i]<-factor(dados1[,i])

hope this helps,

Clem.