问题
What is the reason that lw 0 doesn't have zero linewidth, i.e. invisible?
What I find in the gnuplot manual:
The line width and point size are multipliers for the current terminal's default width ...
Ok, if lw 0 is a multiplier then the resulting linewidth should be zero independent of the terminal's default linewidth.
The reason for asking is to eventually have the possibility to use with linespoints and programmatically switch within a loop between with lines and with points.
Code:
### linewidth 0 isn't zero
reset session
set key out
set yrange[-0.9:10.9]
set ytics 1
plot for [i=0:10] i with lines lw i title sprintf("linewidth %g",i)
### end of code
Result:
By the way, what are the artefacts at the y-axis e.g. at ytics 3,4,6,7,9,10 (wxt-terminal)?
回答1:
Mike Nakis is correct that for at least some of the gnuplot output terminals, including PostScript, gnuplot asks for a 0 width line and the language or library in question interprets that as "1 pixel" or "thinnest possible line".
Similarly "pointtype 0" is not truly missing, it produces a single pixel dot.
You can, however, disable the line drawing altogether by using linetype "nodraw". That gives a complementary pair of commands
plot sin(x) with linespoints lt nodraw pt 7 # only the points are visible
plot sin(x) with linespoints lt 1 pt 0 # only the lines are visible
In some circumstances it may help to know that the numeric equivalent for lt nodraw is lt -2.
回答2:
I don't know for sure what the official explanation is for gnuplot in particular, but in my experience, most graphics packages / tools / libraries etc. use a special convention for a line width of zero.
According to this convention, a line width of zero does not mean invisible; it simply means "the thinnest line possible". This means the thinnest line that can be displayed on the device, regardless of zoom, transformations, logical-to-physical mapping, etc.
So, on monitors, it will be a line which is one pixel wide.
On a printer, it will be the thinnest line that the printer is capable of producing. So, if the printer has a high enough resolution, then the line might practically be invisible, though a magnifying glass should still be able to reveal its existence.
And note that "regardless of zoom, etc." means that even if you set up some scaling that makes your 10-point line look as thick as 100 pixels, the zero-width line will still be exactly one pixel thick.
来源：https://stackoverflow.com/questions/61684554/gnuplot-why-is-linewidth-0-not-zero-in-width