Hi all,

I'm encountering an error with the recent gretl snapshot (v2025c) related to the gnuplot command. The problem arises when using some options like --dummy and/or --factorized with discrete series.

By the way, I realized that the --dummy option is not documented anymore(?) (I am pretty sure it was listed in the past). Probably, this option got superseded by the --factorized option recently (see below).

Below is a minimal example illustrating the issue:

<hansl>
set verbose off
open mrw.gdt --quiet

# "OECD" is a discrete series (see series attributes)
# Note: The following "works" technically, but only 3 data points are shown!
# This used to work in the past:
gnuplot gdpgrow school OECD --dummy --output=display

# This works without error, but again only 3 instead of 121 points are shown
gnuplot gdpgrow school OECD --factorized --output=display

# This returns an error "Invalid argument":
gnuplot gdpgrow school OECD --factorized=OECD --output=display

# After executing the above line, the following also fails with "Invalid argument"
# even though it worked before:
gnuplot gdpgrow school OECD --factorized --output=display
</hansl>

This may be connected to the recent update in version 2025b according to the changelog:

<>
2025-06-05 Version 2025b
- "gnuplot" command: generalize the --dummy functionality for factorized plots; update and improve the help text
</>

I am working under Ubuntu and have gnuplot version 6.0 patchlevel 2 installed

Do you guys face the same error?

Artur