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Asked: 2026-05-16T23:41:12+00:00

I have a dataframe in R with a vector of non-sequential numbers ( data$SiteID

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I have a dataframe in R with a vector of non-sequential numbers (data$SiteID) that i would like to map to a vector of sequential numbers (data$site) to the unique values of data$SiteID. Within each site, I would like to map data$TrtID to 0 where data$TrtID == 'control' or to the next sequential integer, for the other unique data$TrtID‘s:

data <- data.frame(SiteID = c(1,1,1,9,'108','108','15', '15'), 
                   TrtID = c('N', 'control', 'N', 'control', 'P', 'control', 'N', 'P'))
  1. data$site should be c(1,1,1,2,3,3,4,4).
  2. data$trt should be c(1,0,1,0,1,0,0,1).
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1 Answer

  1. Editorial Team

    Use conversion of factors to integers:

    transform(data, site=as.integer(SiteID), trt=as.integer(TrtID))

    If the ordering is important, you can give specific orders to the levels:

    transform(data,
  site = as.integer(factor(SiteID, unique(SiteID))),
  trt  = as.integer(factor(TrtID, unique(c('control', as.character(TrtID))))) - 1L)

    Modified version grouping trt factor by site:

    transform(data,
  site = as.integer(factor(site_id, unique(site_id))),
  trt  = unsplit(tapply(trt_id, site_id, function(x)
         as.integer(factor(x))), site_id) - 1L)
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