通过子集检索 R 中的列值

Question

I have this dataframe (df):

df <- data.frame(Data1 = c(1,3), 
                 Data2 = c(3,9), 
                 Data3 = c(7,2), 
                 Data1Status = c(1,4), 
                 Data2Status = c(2,5), 
                 Data3Status = c(3,6), 
                 NumberOfMaxValue = c(3,2))

Data1  Data2  Data3  Data1Status  Data2Status  Data3Status NumberOfMaxValue
1      3      7      1            2            3           3
3      9      2      4            5            6           2

And i want do get this new column:

Data1  Data2  Data3  Data1Status  Data2Status  Data3Status NumberOfMaxValue  DataMaxStatus
1      3      7      1            2            3           3                 3
3      9      2      4            5            6           2                 5

I tried something like this:

DataMaxStatus = df[, as.numeric(df$NumberOfMaxValue) + 3] , but it didn't work.

EDIT/EXPLANATION:

NumberOfMaxValue is the number of the biggest data (1, 2 or 3)

DataMaxStatus is the status of the greater number between Data1, Data2 e Data3

Answer 1

We can get the corresponding Status value by creating a matrix of row/column index to subset from Status columns.

cols <- grep('Status', names(df))
df$DataMaxStatus <- df[cols][cbind(1:nrow(df), df$NumberOfMaxValue)]
df

#  Data1 Data2 Data3 Data1Status Data2Status Data3Status NumberOfMaxValue DataMaxStatus
#1     1     3     7           1           2           3                3             3
#2     3     9     2           4           5           6                2             5