R help - Feb 2011 - create dummy variables by for loop

HI, Dear R community,

I try to create 100 dummy variables like the following:

ack$id_1 <- (ack$ID==1)*1
ack$id_2 <- (ack$ID==2)*1
..
.
ack$id_100 <- (ack$ID==100)*1


I used the following codes:

for(i in 1:100){
              ack$id_[i] <- (ack$ID==i)*1
                     }

But only one column is created, can anyone help me?

Thanks a lot!


-- 
Sincerely,
Changbin
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r-help-bounces at r-project.org wrote on 02/24/2011 01:23:54 PM:
> [image removed] 
> 
> [R] create dummy variables by for loop
> 
> Changbin Du 
> 
> to:
> 
> <r-help at r-project.org>
> 
> 02/24/2011 01:25 PM
> 
> Sent by:
> 
> r-help-bounces at r-project.org
> 
> HI, Dear R community,
> 
> I try to create 100 dummy variables like the following:
> 
> ack$id_1 <- (ack$ID==1)*1
> ack$id_2 <- (ack$ID==2)*1
> ..
> .
> ack$id_100 <- (ack$ID==100)*1
> 
> 
> I used the following codes:
> 
> for(i in 1:100){
>               ack$id_[i] <- (ack$ID==i)*1
>                      }
This doesn't do what you think it does. when i = 1, it assigns the result 
of (ack$ID==1)*1 to the first element of ack$id_

If you want ack$id_i to be created, try:

ack[[paste("id", i, sep = "_")]] <- (ack$ID==i)*1

> 
> But only one column is created, can anyone help me?
> 
> Thanks a lot!
> 
> 
> -- 
> Sincerely,
> Changbin
> --
> 
>    [[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

On Feb 24, 2011, at 1:23 PM, Changbin Du wrote:
> HI, Dear R community,
>
> I try to create 100 dummy variables like the following:
>
> ack$id_1 <- (ack$ID==1)*1
> ack$id_2 <- (ack$ID==2)*1
> ..
> .
> ack$id_100 <- (ack$ID==100)*1
>
>
> I used the following codes:
>
> for(i in 1:100){
>              ack$id_[i] <- (ack$ID==i)*1
You are creating only one new column named ack$id_

Putting the "[" operator with a numeric argument after does not name a
new column.
>                     }
> But only one column is created, can anyone help me?
If I tell you how to do that I would only be hurting you. You should  
be using factors. The modeling functions should all be capable of  
accepting them and if you are writing your own then it seems only  
sensible that you follow their example.
>

-- 

David Winsemius, MD
West Hartford, CT