[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)]

Hello,

Two alternative approaches - mutate() vs. sapply() - were used to get the desired results (i.e., creating a new column of the most recent date  from 4 dates ) with help from Arun and Mark on this forum.  I now find that the two data objects (created using two different approaches) are not identical although results are exactly the same.  
 
identical(new1, new2) 
[1] FALSE
 
Please see the reproducible example below.

I don't understand why the code returns FALSE here.  Any hints/comments  will be  appreciated.

Thanks,

Pradip

#############################################  reproducible example ########################################
library(dplyr)
# data object - description 

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

# read the data object

example.data <- read.table(textConnection(temp), 
                    colClasses=c("character", "Date", "Date", "Date", "Date"),  
                    header=TRUE, as.is=TRUE
                    )


# create a new column -dplyr solution (Acknowledgement: Arun)

new1 <- example.data %>% 
     rowwise() %>%
      mutate(oldflag=as.Date(max(mrjdate,cocdate, inhdate, haldate,
                                                               na.rm=TRUE), origin='1970-01-01'))

# create a new column - Base R solution (Acknowlegement: Mark Sharp)

new2 <- example.data
new2$oiddate <- as.Date(sapply(seq_along(new2$id), function(row) {
  if (all(is.na(unlist(example.data[row, c('mrjdate','cocdate', 'inhdate', 'haldate')])))) {
    max_d <- NA
  } else {
    max_d <- max(unlist(example.data[row, c('mrjdate','cocdate', 'inhdate', 'haldate')]), na.rm = TRUE)
  }
  max_d}),
  origin = "1970-01-01")

identical(new1, new2) 

# print records

print (new1); print(new2)

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

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Muhuri, Pradip (SAMHSA/CBHSQ)
Sent: Sunday, November 09, 2014 6:11 AM
To: 'Mark Sharp'
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)

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





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