Improve ec() and axis concentration handling

description

• The curves data frame in the output of ecxsys() now contains a column with the concentrations which are used for the plot functions in this package. This is useful for generating a nicer concentration axis.
• Changes to ec():
  • Renamed response_value to effect in the output list.
  • response_level of 0 or 100 is now allowed. 0 returns the concentration 0 and 100 returns the concentration Inf. Previously this resulted in an error.
  • It is now possible to set the reference to a custom value, for example 100.

system details

• RStudio Version: 1.3.937
• R Version: 3.6.3
• OS Version: Windows 10 x64 (build 18363)

checklist

• This merge introduces new features.
  • new features are documented
  • new features have tests
• update documentation including examples (if necessary)
• update and polish NEWS.md
• update version in DESCRIPTION
• update date in DESCRIPTION
• no remaining TODO, FIXME, or debug prints anywhere in the source files
• devtools::document()
• devtools::check() without errors or warnings

added dev documentation enhancement refactoring tests labels

merged

mentioned in commit a1f2a052