adding variable into dataframe by indice

asubs112

  R-Helpers,

  I am trying to insert a value into a dataframe. This value is a
  proportion calculated by counting the number of those individuals
  with that value and then inserting the proportion at the end of the
  dataframe to only those individuals with the given value. The
  problem I am running into is that the proportions are not being
  attached to only those individuals with the specified value for that
  proportion. 

  Below is an example of the code that I am using. The data is made up
  for the dataframe. Should give you an idea, but the original has
  'NA' in many rows. The original data is what is reported in the
  output below.

    #Read in Data
  age.int <- data.frame(IND_ID = seq(1, 140, 10),   rs1042364 =
  sample( c("(1,1)","(1,2)","(2,2)"),14,replace = T), first_drink =
  sample(5:17,14,replace = T))



    asubs112 <- subset(age.int, rs1042364 != "(2,2)")


    ages112 <- sort(unique(na.omit(asubs112$first_drink)))

  for ( i in ages112) {
    indce <- which(na.omit(asubs112$first_drink == i))
    prop <- length(indce)/nrow(asubs112)
    asubs112[indce,4] <- prop
    asubs112[indce,]
  }

  Below is the output that I get from the script above. Notice the
  proportion for the first NA but not any of the others. Not sure what
  I am doing wrong, any suggestions are a big help.

  TIA,
  Adrian

   asubs112[1:50,]
      IND_ID rs1042364 first_drink age_int          V5
4   10008007     (1,2)          NA      16 0.003891051
6   10013012     (1,2)          13      14 0.116731518
7   10015006     (1,2)          12      17 0.105058366
8   10015007     (1,1)          12      16 0.105058366
10  10021009     (1,2)          NA      15          NA
14  10039036     (1,2)          NA      15          NA
15  10039037     (1,2)          NA      13          NA
17  10045005     (1,2)          13      17 0.116731518
18  10045014     (1,2)          13      14 0.116731518
21  10055022     (1,2)          NA      15          NA






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