[R] Creating a new column from a series of columns

[Jorge I Velez]

Dear Dennis,

Assuming that your data.frame() is called dd, the following should get you
started:

colnames(dd[,-1])[apply(dd[,-1], 1, function(x) which(x == 'Yes'))]

HTH,
Jorge.-


On Sat, Nov 1, 2014 at 12:32 PM, Fisher Dennis <fisher at plessthan.com> wrote:

> R 3.1.1
> OS X
>
> Colleagues,
> I have a dataset containing multiple columns indicating race for subjects
> in a clinical trial.  A subset of the data (obtained with dput) is shown
> here:
>
> structure(list(PLTID = c(7157, 8138, 8150, 9112, 9114, 9115,
> 9124, 9133, 9141, 9144, 9148, 12110, 12111, 12116, 12134, 12136,
> 12137, 12142, 12143, 12146, 12147, 13159), Indian..RACE1. = c(NA,
> NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA, NA, NA), Asian..RACE2. = c("", "Yes", "", "", "",
> "", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "",
> ""), Black..RACE3. = c("Yes", "", "", "Yes", "Yes", "Yes", "Yes",
> "Yes", "", "Yes", "", "", "", "", "", "", "", "Yes", "Yes", "",
> "", ""), Native.Hawaiian.or.other.Pacif..RACE4. = c(NA, NA, NA,
> NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA), White..RACE5. = c("", "", "Yes", "", "", "", "",
> "", "Yes", "", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes", "Yes",
> "", "", "Yes", "Yes", "Yes"), Other.Race..RACE6. = c(NA, NA,
> NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA, NA), Specify.Other.Race..RACEOTH. = c(NA, NA, NA,
> NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
> NA, NA, NA)), .Names = c("PLTID", "Indian..RACE1.", "Asian..RACE2.",
> "Black..RACE3.", "Native.Hawaiian.or.other.Pacif..RACE4.", "White..RACE5.",
> "Other.Race..RACE6.", "Specify.Other.Race..RACEOTH."), class =
> "data.frame", row.names = 43:64)
>
> I would like to add a column that indicates which of the other columns
> contains "Yes".  In other words, that column would contain:
>         Black..RACE3.
>         Asian..RACE2.
>         White..RACE5.
>         Black..RACE3.
>         ...
>
> Even better would be
>         Black
>         Asian
>         White
>         Black
>         ...
> (which I can accomplish with strsplit)
>
> None of the rows contains more than one 'Yes' although it is possible that
> none of the entries in a row would be 'Yes' (in which case, the entry in
> the new column should be NA)
>
> I could do this by looping through each of the columns with something like
> this:
>         DATA$RACE               <- NA
>         for (COL in 2:8)        DATA$RACE[which(DATA[,COL] == "Yes")]   <-
> names(DATA)[COL]
> But, I suspect that there is some more elegant way to accomplish this.
>
> Thanks in advance.
>
> Dennis
>
> Dennis Fisher MD
> P < (The "P Less Than" Company)
> Phone: 1-866-PLessThan (1-866-753-7784)
> Fax: 1-866-PLessThan (1-866-753-7784)
> www.PLessThan.com
>
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