[R] Getting the most recent dates in a new column from dates in four columns using the dplyr package (mutate verb)

[Mark Sharp]

Pradip,

mutate() works on the entire column as a vector so that you find the maximum of the entire data set.

I am almost certain there is some nice way to handle this, but the sapply() function is a standard approach.

max() does not want a dataframe thus the use of unlist().

Using your definition of data1:

data3 <- data1
data3$oidflag <- as.Date(sapply(seq_along(data3$id), function(row) {
  if (all(is.na(unlist(data1[row, -1])))) {
    max_d <- NA
  } else {
    max_d <- max(unlist(data1[row, -1]), na.rm = TRUE)
  }
  max_d}),
  origin = "1970-01-01")

data3
  id    mrjdate    cocdate    inhdate    haldate    oidflag
1  1 2004-11-04 2008-07-18 2005-07-07 2007-11-07 2008-07-18
2  2       <NA>       <NA>       <NA>       <NA>       <NA>
3  3 2009-10-24       <NA> 2011-10-13       <NA> 2011-10-13
4  4 2007-10-10       <NA>       <NA>       <NA> 2007-10-10
5  5 2006-09-01 2005-08-10       <NA>       <NA> 2006-09-01
6  6 2007-09-04 2011-10-05       <NA>       <NA> 2011-10-05
7  7 2005-10-25       <NA>       <NA> 2011-11-04 2011-11-04



R. Mark Sharp, Ph.D.
Director of Primate Records Database
Southwest National Primate Research Center
Texas Biomedical Research Institute
P.O. Box 760549
San Antonio, TX 78245-0549
Telephone: (210)258-9476
e-mail: msharp at TxBiomed.org





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