[R] Dummy (factor) based on a pair of variables

[Jason Morgan]

On 2009.04.18 13:52:35, Serguei Kaniovski wrote:
> Bernardo: this is not quite what I am looking for,
> 
> Let the data be:
> y,i,j
> 1,AUT,BEL
> 2,AUT,GER
> 3,BEL,GER
> 
> then the dummies sould look like:
> 
> y,i,j,d_AUT,d_BEL,d_GER
> 1,AUT,BEL,1,1,0
> 2,AUT,GER,1,0,1
> 3,BEL,GER,0,1,1
> 
> I can generate the above dummies but can this design be imputed in a 
> reg. model directly?
> 
> Serguei

Hello Serguei,

I am sure there is a better way to do this, but the following seems to
work:

# Create sample data.frame()
i  <- c("AUT", "AUT", "BEL")
j  <- c("BEL", "GER", "GER")
df <- data.frame(i=i, j=j)

# Create dummy vectors
df$d.aut <- ifelse(df$i=="AUT"|df$j=="AUT", 1, 0)
df$d.bel <- ifelse(df$i=="BEL"|df$j=="BEL", 1, 0)
df$d.ger <- ifelse(df$i=="GER"|df$j=="GER", 1, 0)

# Print results
df

HTH,

~Jason


--
Jason W. Morgan
Graduate Student, Political Science
*The Ohio State University*