Realtime Optimized Linear Regression Channel

this script is based on "Optimized Linear Regression Channel" by alexgrover, whose page I recommend you to visit, to read the extensive description he provides

the main difference with the original version is the fact that the start point of the channel (left point) is fixed by setting the time (Begin time input).
This way, the channel size is automatically set, meaning that the channel grows larger as new data comes in, while the starting point remains at the same spot

this can be useful to track a new trend that may be forming from an inflection point or pivot, by selecting begin time as the time of the inflection

also, an end date input is provided to limit the size of the channel.

The script provides two channels:

• the main channel that contain all data from begin to end time
  
• the best fit channel that finds the best linear fit inside data from begin to end time
  

one issue that the script has is the limit in the number of points of size of the channel, that if too large then make the channel disappear (sigh)

Versionshinweise:

• Added the possibility to choose which channel to show (or both)
  
• Added the possibility to choose color and style for lines of the channels
  

Versionshinweise:

Converted to pinescript v5 ...

Versionshinweise:

• solved the issue of the limit in bars back
  
• now by default the beginning of the channel is set to today's first bar, see the new input tick