Comparing Multiple Dates
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Does anyone know of a way to compare multiple dates (or other values) across variables? What I have are three different date variables, and I want to identify (for each case) the most recent of the three dates. In addition, one or more of the values can be null for any particular case. I am told that in SAS it is possible in a single command to ask for the most recent value of multiple variables. But with SPSS, as far as I have been able to figure, I need to use the brute force method of writing dozens of lines of DO IF-ELSE IF code to encompass all possibilities of null and present values, plus running one-by-one comparisons (if Date1 > Date2 and Date1 > Date3, choose Date1, if Date1 > Date2 and Date3 > Date1, choose Date3, etc.). I realize another way would be to run VARS to CASES and transform all three date variables into a single variable and then sort and select for most recent, but this strikes me as more cumbersome and prone to error than the brute force method. I searched on the archive and in the manuals and on the web, but found no simpler approach. But I hope I am missing something. Thank you, and be well! Alan Alan D. Krinsky PhD, MPH
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Why not just use max(date1, date2, date3)?
Jon Peck Senior Software Engineer, IBM [hidden email] new phone: 720-342-5621 From: "Krinsky, Alan" <[hidden email]> To: [hidden email] Date: 08/09/2011 08:11 AM Subject: [SPSSX-L] Comparing Multiple Dates Sent by: "SPSSX(r) Discussion" <[hidden email]> Does anyone know of a way to compare multiple dates (or other values) across variables? What I have are three different date variables, and I want to identify (for each case) the most recent of the three dates. In addition, one or more of the values can be null for any particular case. I am told that in SAS it is possible in a single command to ask for the most recent value of multiple variables. But with SPSS, as far as I have been able to figure, I need to use the brute force method of writing dozens of lines of DO IF-ELSE IF code to encompass all possibilities of null and present values, plus running one-by-one comparisons (if Date1 > Date2 and Date1 > Date3, choose Date1, if Date1 > Date2 and Date3 > Date1, choose Date3, etc.). I realize another way would be to run VARS to CASES and transform all three date variables into a single variable and then sort and select for most recent, but this strikes me as more cumbersome and prone to error than the brute force method. I searched on the archive and in the manuals and on the web, but found no simpler approach. But I hope I am missing something. Thank you, and be well! Alan
Alan D. Krinsky PhD, MPH
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In reply to this post by Krinsky, Alan-2
Hi Alan,
I don't know what you mean by 'null' value. I'll assume you
mean 'system missing' value.
If you just want to find the most recent, i.e., the largest,
date stored in a given set of variables, i think the max function is what you
need. However, if you also want to know which variable in the given set of
variables contains the most recent value, something more complicated is
required.
Gene Maguin From: SPSSX(r) Discussion [mailto:[hidden email]] On Behalf Of Krinsky, Alan Sent: Tuesday, August 09, 2011 9:24 AM To: [hidden email] Subject: Comparing Multiple Dates Does anyone know of a way to compare multiple dates (or other values) across variables? What I have are three different date variables, and I want to identify (for each case) the most recent of the three dates. In addition, one or more of the values can be null for any particular case. I am told that in SAS it is possible in a single command to ask for the most recent value of multiple variables. But with SPSS, as far as I have been able to figure, I need to use the brute force method of writing dozens of lines of DO IF-ELSE IF code to encompass all possibilities of null and present values, plus running one-by-one comparisons (if Date1 > Date2 and Date1 > Date3, choose Date1, if Date1 > Date2 and Date3 > Date1, choose Date3, etc.). I realize another way would be to run VARS to CASES and transform all three date variables into a single variable and then sort and select for most recent, but this strikes me as more cumbersome and prone to error than the brute force method. I searched on the archive and in the manuals and on the web, but found no simpler approach. But I hope I am missing something. Thank you, and be well! Alan Alan D. Krinsky PhD, MPH |
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