st: solution to my question: separating string of fixed length into sections

[Michael McCulloch <mm@pinest.org>]

I'd like to share what I learned (and thanks to Maarten Buis who suggested 
using -destring- in combination with the floor function.)

I have a date string which I'd like to convert to Stata date.

Before I can use mdy() and date(), I need to split the string into sections:
        the first four characters for year,
        then the next two for month,
        then the last two for day.


. tostring datedx, replace
. generate str4 dxyr = substr(datedx,1,4)
. generate str2 dxmo = substr(datedx,5,6)
. generate str2 dxda = substr(datedx,7,8)
. destring dx*, replace
. gen edate = mdy(dxmo, dxda, dxyr)
. format edate %d
. list datedx edate dxyr dxmo dxda in 1/5
     +-------------------------------------------+
     |   datedx       edate   dxyr   dxmo   dxda |
     |-------------------------------------------|
  1. | 19900417   17apr1990   1990      4     17 |
  2. | 19880107   07jan1988   1988      1      7 |
  3. | 19930407   07apr1993   1993      4      7 |
  4. | 19880819   19aug1988   1988      8     19 |
  5. | 19890127   27jan1989   1989      1     27 |
     +-------------------------------------------+



AND, Maarten's suggestion for using -destring- in combination with the 
floor function:

You can achieve what you want by using the dates as numbers (i.e. use
-destring- first) in combination with the floor function. See the
example below:

.destring datedx, replace
.gen int year = floor(datedx/10000)
.gen int month = floor((datedx-year*10000)/100)
.gen int day = datedx - year*10000 - month*100
.list datedx year month day in 1/5
     +-------------------------------+
     |   datedx   year   month   day |
     |-------------------------------|
  1. | 19900417   1990       4    17 |
  2. | 19880107   1988       1     7 |
  3. | 19930407   1993       4     7 |
  4. | 19880819   1988       8    19 |
  5. | 19890127   1989       1    27 |
     +-------------------------------+




Best wishes,
Michael


____________________________________

Michael McCulloch
Pine Street Clinic
Pine Street Foundation
124 Pine Street, San Anselmo, CA 94960-2674
tel     415.407.1357
fax     415.485.1065
email:  mm@pinest.org
web:    www.pinest.org
        www.pinestreetfoundation.org
        www.medepi.net/meta





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