topic Re: Creating time intervals for longitudinal data, and taking averages within intervals in SAS Programming

Creating time intervals for longitudinal data, and taking averages within intervals

luch25 — Sat, 29 Jan 2022 18:11:29 GMT

Hello all,

I'm looking for some advice on how to go about coding this. I have a dataset with longitudinal measurements of heart rate (HR) and respirations (resp). Each individual (ID) has multiple measurements. The three main things I need to do are:

By unique ID, flag measurements that are taken within 5 minutes of each other (flag=1)
For measurements that are NOT taken within 5 minutes of another measurement, retain the original value of HR and resp.
For measurements that are taken within 5 minutes of each other, apply these rules to produce the final dataset
1. If there are 2 measurements within the 5-minute interval, take the average of the measurements, as well as the datetime value to produce a new value
2. If there are >2 measurements within the 5-minute interval, delete the first value, and take the average fo the remaining measurements.

Code for an example dataset are provided below. I've also provided a description of "what's going on" for each individual below the code.

data have;
	input id datetime hr resp;
	format datetime datetime22.3.;
	cards;
1 19MAR2009:13:15:00.000 90 16
1 19MAR2009:13:17:00.000 70 18
1 19MAR2009:13:18:00.000 80 17
1 19MAR2009:13.22:00.000 100 22
1 23MAR2009:10:36:00.000 83 21
2 29OCT2009:10:36:00.000 121 13
2 29OCT2009:10:38:00.000 83 14
2 08JUL2011:13:04:00.000 131 18
3 07SEP2016:14:26:59.000 50 12
3 06APR2017:13:39:00.000 76 18
3 08JUL2017:13:04:00.000 98 17
3 08JUL2017:13:08:00.000 96 18
3 24OCT2017:15:11:00.000 80 19
4 18APR2012:08:42:00.000 80 17
4 31OCT2012:10:36:00.000 96 19
4 31OCT2012:10:37:00.000 103 21
4 31OCT2012:10:38:00.000 105 25
4 31OCT2012:10:39:00.000 110 28
5 06JAN2008:05:37:00.000 98 17
5 15FEB2010:10:24:00.000 110 18
;

ID=1 has two "5 minute intervals". The first 3 measurements make up one interval (delete the one at 13:15 and take the average of 13:17 and 13:18. Then the 2nd, 3rd, and 4th measurements make up a second interval (delete the one at 13:17, and take the average of 13:18 and 13:22).
ID=2 has one "5 minute interval" with 2 measurements, so take the average of these two
ID=3 has two measurements within a "5 minute interval"
ID=4 has 4 measurements within a "5 minute interval". Delete the one at 10:36 and take the average of the remaining ones
ID=5 does not have any measurements within a 5 minute interval
And as you can see, I want to retain measurements even if they are not in the 5 minute interval (flag=0)!

Applying these rules, this is what I envision the final dataset looking like:

ID	Datetime (format=datetime22.3)	HR2	Resp2	Flag
1	19MAR2009:13:17:30.000	75	17.5	1
1	19MAR2009:13.19:00.000	83.3	19	1
1	23MAR2009:10:36:00.000	83	21	0
2	29OCT2009:10:37:00.000	102	13.5	1
2	08JUL2011:13:04:00.000	131	18	0
3	07SEP2016:14:26:59.000	50	12	0
3	06APR2017:13:39:00.000	76	18	0
3	08JUL2017:13:06:00.000	97	17.5	1
3	24OCT2017:15:11:00.000	80	19	0
4	18APR2012:08:42:00.000	80	17	0
4	31OCT2012:10:37:30.000	103.5	23.25	1
5	06JAN2008:05:37:00.000	98	17	0
5	15FEB2010:10:24:00.000	110	18	0

Any advice on how to handle this would be hugely appreciated! Thank you in advance!

Re: Creating time intervals for longitudinal data, and taking averages within intervals

PeterClemmensen — Sat, 29 Jan 2022 18:32:18 GMT

First of all, thank you for providing usable sample data and a clear explanation 🙂

Secondly. When two obs are within 5 min of each other, these two obs should become 1 obs, correct?

Re: Creating time intervals for longitudinal data, and taking averages within intervals

luch25 — Sat, 29 Jan 2022 18:43:41 GMT

Thank you for the clarification! Yes, that is correct. If there are two observations within 5 minutes of each other, they should effectively become a single (averaged) observation in the new dataset. The datetime variable would also be averaged.

The caveat is if there are >2 observations within 5 minutes of each other, the first observation is completely deleted. Then the remaining observations are averaged into a single observation. So if there are 3 measurements within 5 minutes, they become 1; if there are 4 measurements, they also become 1; etc.

Re: Creating time intervals for longitudinal data, and taking averages within intervals

luch25 — Mon, 31 Jan 2022 00:08:29 GMT

@PeterClemmensen Any advice on how to approach this problem? Even just the first step of creating the 5-minute time interval flags indicating that there are multiple observations. Thank you!

Re: Creating time intervals for longitudinal data, and taking averages within intervals

PeterClemmensen — Mon, 31 Jan 2022 07:26:06 GMT

@luch25, sure just been busy. I'll post a solution during the day 🙂

Re: Creating time intervals for longitudinal data, and taking averages within intervals

luch25 — Mon, 31 Jan 2022 12:07:33 GMT

Oh it's no problem at all! Take your time. Just sounded like you were onto something 🙂

Re: Creating time intervals for longitudinal data, and taking averages within intervals

luch25 — Mon, 31 Jan 2022 12:08:18 GMT

Oh it's no problem at all! Take your time. Just sounded like you were onto something 🙂