Changes in version 0.1.6                        

  - added new functions max2/min2 reutrn NA instead of Inf/-Inf

                 Changes in version 0.1.5 (2023-08-10)                  

  - the 'to' argument in date_from function supports vector
  - added an inner function dat_filter to filter data set by given date
    range

                 Changes in version 0.1.4 (2023-04-11)                  

  - fixed a bug in the date_num function

                 Changes in version 0.1.3 (2022-12-25)                  

  - added a new function date_num to convert date to number
  - fixed a few bugs

                 Changes in version 0.1.2 (2022-11-26)                  

  - added cols_type and cols_const function
  - fixed a bug in date_from function

                 Changes in version 0.1.1 (2022-07-03)                  

  - Fixed a few bugs

                 Changes in version 0.1.0 (2022-05-17)                  

  - Initial version