[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)]

Hi Mark,

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

Regards,

Pradip

Pradip K. Muhuri, PhD
SAMHSA/CBHSQ
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)

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





NOTICE:  This E-Mail (including attachments) is confidential and may be legally privileged.  It is covered by the Electronic Communications Privacy Act, 18 U.S.C.2510-2521.  If you are not the intended recipient, you are hereby notified that any retention, dissemination, distribution or copying of this communication is strictly prohibited.  Please reply to the sender that you have received this message in error, then delete it.