Background

You have a series of Points and want to select a sub-set of Points from that series.  

Steps to Accomplish

Method 1:

If we need to select the first few points in a point series, we can do it by using the below expression:

Point1.First(10)

This means the selected points will be the first 10 points of the series (Point1[0] to Point1[9])

To identify the sub-set of points, we will create vertical lines on those selected Points. Here Point1 is the set of points and it begins from left to right. (The same process will also be followed in the below mentioned methods)

Method 2:

If we need to select the last few points in a point series, we can do it by using the below expression:

Point1.Last(5)

This means the selected points will be last 5 points of the series.

Method 3 :

If we need to select points in the middle of a point series, we can do it by using the below expression: 

Point1.First(10).Last(6)

This means the selected points will be Point1[4] to Point1[9]. In this expression the selection of points will begin with point number 9, as 10 is an argument to the list method, and the last "(6)" designates the number of points that will be taken in the set. That means point 4, point 5, point 6 -- through point 9 will be selected.

Please go through the sample file,  https://communities.bentley.com/cfs-file/__key/communityserver-wikis-components-files/00-00-00-00-28/Selection-of-Points-by-Range-Indices.gct

Note: 

For OBD Update 7 and later versions the First has been changed to Take and Last has been changed to TakeLast. The functionality is similar as the previous functions, only the name of the functions have been changed.