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Editorial Team
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Asked: 2026-06-08T11:20:52+00:00

I’ve got a dataframe that looks like MAP name series ID 1.0 aspartame baseline

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I’ve got a dataframe that looks like

MAP  name       series    ID
1.0  aspartame  baseline  902349
1.0  aspartame  baseline  82749
1.0  aspartame  baseline  928542
1.0  aspartame  next      928542
0.8  aspartame  next      82749
0.8  aspartame  next      902349

And I’d like to join this data on ID and calculate the difference
between baseline and next in the MAP score. so this should give

diff name       ID
0.2  aspartame  902349
0.2  aspartame  82749
0.0  aspartame  928542
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1 Answer

  1. Editorial Team

    As requested by OP: A solution using reshape (or rather reshape2).

    d <- read.table(text = "
MAP  name       series    ID
1.0  aspartame  baseline  902349
1.0  aspartame  baseline  82749
1.0  aspartame  baseline  928542
1.0  aspartame  next      928542
0.8  aspartame  next      82749
0.8  aspartame  next      902349", header = TRUE)

require(reshape2)

dcast(data = d, formula = ID  + name~ ., value.var = "MAP", 
      fun.aggregate = function(x) (x[1] - x[2]))

    gives

          ID      name  NA
1  82749 aspartame 0.2
2 902349 aspartame 0.2
3 928542 aspartame 0.0
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