Follow-up to automatic trim functions or to be used manually, will
display a plot with the density profiles. Most commonly used in
automatic failure corrections by the function correct_failures. Use
your mouse to select starting/ending point on the plot, your
selection will then be displayed on the plot. Either returns a
numeric value or NA in case of errors. There are two special cases:
when encountering an error with a label = " - PICK START" it will
return the starting position, and with label " - PICK STOP" it will
return the ending position. These labels are used when correcting
several density profiles at once using correct_failures.
This function uses graphics::locator, which only works on
screen devices X11, windows and quartz. It will not work on other
devices, returning NA.