Version 1.3.0 - 2024-08-16
  - Fixed messy mata error when only a single event.
  - The list() option now lists RS beyond last event if there is a censoring
    observation greater than the listed value.
  - Minor change in calculation of crude probabilities when not using 
    reference adjustment (difference is at 3rd/4th decimal place).

Version 1.2.7 - 2023-02-21
  - New option frame() to save results of list option to a frame.

Version 1.2.6
  - Use of the by option without the list option gave an unhelpful error. Now Fixed.

Version 1.2.5
  - Add minexpsurv and dropexpected options

Version 1.2.4
  - Add better return matrices when using by option

Version 1.2.3 - 2021-10-14
  - fixed mata error when having a time in list() option less than first event

Version 1.2.2 - 2021-08-16
  - removed output from error checks
  - better check for no events

Version 1.2.1 - 2021-08-15
  - updated variance estimation for crude probabilities of death
  - added levels option
  - Use of if statement returned unnecessary values  
  - Improved error checks

Version 1.2.0 - 2021-06-08
  - fixed links for example code in help file

Version 1.1.9 - 2021-06-04
  - graph options added by Mark Rutherford

Version 1.1.8 - 2021-02-10
  - stpp gave an unuseful mata error with delayed entry. This has been fixed. 

Version 1.1.7 - 2020-12-22
  - When listing results on the screen using the list() option, a missing
    value was given if the time was greater than the largest event time,
    but less than the largest censoring time. This has been fixed.

Version 1.1.6 - 2020-12-13
  - Fixed mata error when list() option had time greater than in data
  - some minor speed gains
  - help file examples now produce nice graphs (previously not sorted by _t)

Version 1.1.5 - 2020-10-19
  - fixed bug introduced in 1.1.4: ederer2 option now works again.

Version 1.1.4 - 2020-10-06
  - check for problems with merging lifetable
  - Big speed up in writing results back to Stata
  - Change default for transformation to survival to product integration.
     (added "fh" option for Fleming-Harrington estimates)

Version 1.1.2 - 2020-07-14
  - changed weights for references adjusted measures
  - added error if try to use ederer2 option with using2()