[plot.STM] type = " perspectives" what is black dashed line in plot

[SOLBINLEE]

Hi, and thanks for an excellent package!

I'm trying to run the plot.STM function with type = "perspectives".

I got a results. so I read the manual to interpret the results.

The manual is described as follows.

Words aresized proportional to their use within the plotted topic-covariate combinations and oriented along
the X-axis based on how much they favor one of the two configurations. If the words cluster on top
of each other the user can either set the plot size to be larger or shrink the total number of words
on the plot.

**The manual does not describe vertical black dashed lines of the X-axis

I wonder what the vertical black dashed line of the X-axis is**

Many thanks for help!