[R] Subseting by more than one factor...

[Fernando Henrique Ferraz Pereira da Rosa]

  Is it possible in R to subset a dataframe by more than one factor, all at
once?
     For instance, I have the dataframe: 
 >data 
   p1 p2 p3 p4 p5 p6 p7 p8 p9 p10      pred
  1    0  1  0  0  0  0  0  0  0   0 0.5862069
  4    0  0  0  0  0  0  0  0  0   1 0.5862069
  5    0  0  0  0  0  0  1  0  0   0 0.5862069
  6    0  0  0  0  0  0  0  1  0   0 0.5862069
  7    0  0  1  0  0  0  0  0  0   0 0.5862069
  9    0  0  0  0  1  0  0  0  0   0 0.5862069
  20   0  1  1  0  0  0  0  0  0   0 0.5862069
  22   0  1  0  0  1  0  0  0  0   0 0.5862069
  24   0  1  0  0  0  0  1  0  0   0 0.5862069
  25   0  1  0  0  0  0  0  1  0   0 0.5862069
  27   0  1  0  0  0  0  0  0  0   1 0.5862069

  If I want to subset only those points that have p4 = 1, I do:
   > subset(data,p4 == 1)
  And that's fine. Now suppose I want to subset those that not only have p4
= 1, but also p6 = 1.
   I tried subset(data,p4 == 1 && p6 == 1) or subset(data,p4==1 & p6==1).
But it didn't work.
   Then I found a clumsy way to do it :
    subset(subset(data,p4==1),p6==1)
    Which works. But it soon gets very clumsy as the number of conditions
increase (I end up with a really large number of nested subsets). Is there a
simpler way to do that?


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