Dear R help,

 

I am fairly new in data management and programming in R, and am trying to write what is probably a simple loop, but am not having any luck. I have a dataframe with something like the following (but much bigger):

 

Dates<-c("12/10/2010","12/10/2010","12/10/2010","13/10/2010", "13/10/2010", "13/10/2010")

Groups<-c("A","B","B","A","B","C")

data<-data.frame(Dates, Groups)

 

I would like to create a new column in the dataframe, and give each distinct date by group a unique identifying number starting with 1, so that the resulting column would look something like:

 

ID<-c(1,2,2,3,4,5)

 

The loop that I have started to write is something like this (but doesn't work!):

 

data$ID<-as.number(c()) 

for(i in unique(data$Dates)){

  for(j in unique(data$Groups)){ data$ID[i,j]<-i

  i<-i+1

  }

}

 

Am I on the right track?

 

Any help on this is much appreciated!

 

Chandra


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