[R] R help - Adding a column in a data frame with multiple conditions

[Sarah Goslee]

Hi Libby,

You had an accumulation of small errors, from an extra ) to an unclear
understanding of how indexing works in R. Also, you shouldn't call
your dataframe df, or use square brackets in column names.

That said, what about:


sampledata <- structure(list(A = c(1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L,
3L), B = c("X",
"Y", "Z", "X", "Y", "Z", "X", "Y", "Z"), C = c(90L, 72L, 67L,
74L, 42L, 81L, 92L, 94L, 80L), D = c(88L, 70L, 41L, 49L, 50L,
56L, 59L, 80L, 82L)), .Names = c("A", "B", "C", "D"), class =
"data.frame", row.names = c(NA,
-9L))

E <-
ifelse((sampledata$A == 1) & (sampledata$B == "X"), sampledata$C,
ifelse((sampledata$A == 1) & (sampledata$B == "Y"), sampledata$D,
ifelse((sampledata$A == 1) & (sampledata$B == "Z"),  sampledata$C, NA)))

sampledata <- data.frame(sampledata, E)

Sarah

On Thu, Oct 4, 2012 at 2:47 PM, Libby M Gertken <libbymg at utexas.edu> wrote:
> Hi,
>
> I am trying to add a column of numbers to a data frame in R with multiple
> conditions.
>
> Here is a simplified example df:
>
> [A]  [B] [C] [D] [E]
> [1] 1 X 90 88
> [2] 1 Y 72 70
> [3] 1 Z 67 41
> [4] 2 X 74 49
> [5] 2 Y 42 50
> [6] 2 Z 81 56
> [7] 3 X 92 59
> [8] 3 Y 94 80
> [9] 3 Z 80 82
>
> I would like column [E] to have a certain value (found either in [C] or
> [D]) based on conditions in columns [A] *and* [B].
>
> E.g. :
> if [A] = 1 and [B] = X, then [E] = the entry in [C] for that row (i.e., 90)
> if [A] = 1 and [B] = Y, then [E] = the entry in [D] for that row (i.e., 70)
> if [A] = 1 and [B] = Z, then [E] = the entry in [C] for that row (i.e., 67)
>
> if [A] = 2 and [B] = X, then [E] = the entry in [C] for that row (i.e., 74)
> if [A] = 2 and [B] = Y, then [E] = the entry in [D] for that row (i.e., 50)
> if [A] = 2 and [B] = Z, then [E] = the entry in [C] for that row (i.e., 81)
>
> and so on.
>
> ATTEMPT TO RESOLVE:
>
> The following code allowed me to add values for column [E] when [A] ==1,
> but I can't figure out how to keep the code going in order to get a value
> for column [E] based on all of the numbers in column [A] and the secondary
> condition for [B] ([A] goes from 1:48).
>
> df$[E] <-
>
>
> ifelse((df$A == 1) & (df$B == "X"), df$C[df$A == 1],
>
> ifelse((df$A == 1) & (df$B == "Y"), df$D[df$A == 1],
>
> ifelse((df$A == 1) & (df$B == "Z"),  df$C[df$A == 1],
>
> NA))))
>
>
> Thank you for any advice you can give.
>
>
> Libby G
>
> libbymg[at]utexas.edu
>
>         [[alternative HTML version deleted]]
>
-- 
Sarah Goslee
http://www.functionaldiversity.org