How to create a Variable that measures the time difference between two variables?

[marysmith]

data patients1; 
set patients;
format authorisation ddmmyy10.;
if NIS_Nummer in (2628,3078,6791) then authorisation='11Jan2008'd;
if NIS_Nummer in (2408) then authorisation='28Aug2007'd;
if NIS_Nummer in (6759) then authorisation='18Sep2014'd;
if NIS_Nummer in (2311,5361,6887) then authorisation="23Apr2007"d;
if NIS_Nummer in (6687) then authorisation="03Aug2009"d;
if NIS_Nummer in (6667) then authorisation="27May2015"d;
run;

data datensatz_pms; 
set datensatz_pms;
format n_date ddmmyy10.;
n_date = input(notificationdate,ddmmyy10.);
if '01jan2013'd <= n_date <= '31dec2013'd then year=2013;
if '01jan2014'd <= n_date <= '31dec2014'd then year=2014;
if '01jan2015'd <= n_date <= '31dec2015'd then year=2015;
if '01jan2016'd <= n_date <= '31dec2016'd then year=2016;
if '01jan2017'd <= n_date <= '31dec2017'd then year=2017;
run;                                                    

Dear community,

thank you for your instant support when i am struggeling with sas.

I need your help again.

Now I have to measure the difference between two date Variables (notification date and authorisation date) and if the time difference between the authorisation date and the notification date is shorter than 2 years I its a newly authorised drug and if the time difference is longer than 2 years its not a newly authorised drug. I need Sas to create me a new variable with that information(newly authorised: yeys/no). But how to create this variable?

I really need your support with this as I have absolutely no idea^^

[PeterClemmensen]

Subtract the two dates from each other or use the INTCK Function to measure how many specified intervals there are between two dates like this

data test;
days=intck('day','01jan2009'd,'01jan2018'd);
weeks=intck('week','01jan2009'd,'01jan2018'd);
months=intck('month','01jan2009'd,'01jan2018'd);
years=intck('year','01jan2009'd,'01jan2018'd);
run;

[marysmith]

How do I use it with those two variables?
Like this?
data patients_new;
set patients
days=intck('authorisationdate', '01aug2011'd,'notificationdate' '01feb2012'd);
put days=;
run;

[PeterClemmensen · Accepted solution]

No. If you have two date variables, lets say date1 and date2 in a data set like this

data dates;
date1='01jan2009'd;
date2='01jan2018'd;
format date: date9.;
run;

and you want to calculate the difference between them, measured in years, do like this

data want;
   set dates;
   yearsbetween=intck('year',date1,date2);
run;

Change the first argument in the INTCK Function to day, week, month or whatever interval you want to measure.

[marysmith]

Ok thanks! But I already have the 2 variables with the dates for all 260 cases. My dataset looks like that. And now I need sas to substrate those two dates for all 260 cases and create me a new variable (new_authorised:0/1)
Number authorization notificationdate new_auth
1 12/02/2008 10/05/2014 0
2 15/06/2004 02/02/2015 0
3 07/08/2013 21/10/2014 1

[PaigeMiller]

Are these actually SAS dates in your data set, or are the character strings? Are the variables character or numeric?

[PaigeMiller]

You subtract one date from the other. This assumes your variables are SAS date values. Then you can see if that value is >730 (which is two years in days).

If you need more details, you have to provide more details, and show us a small portion of the relevant data.

[marysmith]

Thank you!
But how to substract those two variables? What information do you need?

[PeterClemmensen]

data dates;
date1='01jan2009'd;
date2='01jan2018'd;
daysbetween=date2-date1;
run;

[marysmith]

Oh yeah that was easy^^ thank you 🙂