Count observations and delete all but the last observation

[Anonymous10]

I have a table of meetings that contains meeting information.

However some meetings are rescheduled for a new time or date. These meetings appear twice or more in the dataset.

I want to keep only the information for the last meeting, however I would like to store the information on how many times the meeting have been rescheduled.

How can I achieve this in SAS?

The key data that I have is:

MeetingID                          CustID                 Meetingdate    MeetingTime

Timestamp at booking         ID                            Date              Time

What I want:

CustID                      Meetingdate          Meetingtime        Number of reschedules

ID                                   Date                       Time                     #

I realize that if a meeting is rescheduled it can still appear twice, however this is a only a minor issue.

If there is a smart solution to allow to count rescheduled meetings say within +-15 days this would be excellent, but not a necessary requirement. 

CustID                      Meetingdate          Meetingtime        Number of reschedules on this date        Meetings within +-15 days

ID                                   Date                       Time                          #                                                                     #

As I am new to SAS i'm not able to achieve this by code, hopefully someone has a smart solution.

I'm using SAS EG 8.2.

[Kurt_Bremser · Accepted solution]

First, sort by meeting ID and meeting date/time

Then do

data want;
set have;
by meeting_id;
if first.meeting_id
then reschedules = 0;
else reschedules + 1; /* use of sum statement causes automatic retain */
if last.meeting_id; /* only keep last observation of a group */
run;

For tested code, supply example data in usable form, as a data step with datalines.