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

Muhuri, Pradip (SAMHSA/CBHSQ) Pradip.Muhuri at samhsa.hhs.gov
Sun Nov 9 12:11:07 CET 2014

Hi Mark,

Your code has also given me the results I expected.  Thank you so much for your help.



Pradip K. Muhuri, PhD
1 Choke Cherry Road, Room 2-1071
Rockville, MD 20857
Tel: 240-276-1070
Fax: 240-276-1260

-----Original Message-----
From: Mark Sharp [mailto:msharp at TxBiomed.org] 
Sent: Sunday, November 09, 2014 3:01 AM
To: Muhuri, Pradip (SAMHSA/CBHSQ)
Cc: r-help at r-project.org
Subject: Re: [R] Getting the most recent dates in a new column from dates in four columns using the dplyr package (mutate verb)


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)
  origin = "1970-01-01")

  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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