[R] simplifying the code

[alex diaz]

dear list:

I need help to achieve a simpler code to complete a 
task I'm performing.
here is an example:

dat<-expand.grid(a=seq(1,5),b=seq(1000,1005))

I want to add a new column dat$c in that:

t1<-ifelse(dat$a==1&dat$b==1001,1001,0)
t2<-ifelse(dat$a==2&dat$b==1002,1001,0)
t3<-ifelse(dat$a==3&dat$b==1003,1001,0)
t4<-ifelse(dat$a==1&dat$b==1002,1002,0)
t5<-ifelse(dat$a==2&dat$b==1003,1002,0)
t6<-ifelse(dat$a==1&dat$b==1003,1003,0)
dat$c<-t1+t2+t3+t4+t5+t6


My real data frame is much larger... I hope someone 
can help me with this.

thanks for your help

a. diaz

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