问题
I would like to add a horizontal line in my histogram in gnuplot, is that possible?
My histogram has on the x axis: alea1 alea 2 alea3 nalea1 nalea 2 nalea 3 and the y axis goes from 0 to 25.
At 22, I want to add a horizontal line that goes all the way across from one end to the other end of the histogram.
回答1:
Try adding
, 22 title ""
at the end of your plot command. Works for my test data (file "histo"):
# Year Red Green Blue
1990 33 45 18
1991 35 42 19
1992 34 44 14
1993 37 43 25
1994 47 15 30
1995 41 14 32
1996 42 20 35
1997 39 21 31
plot "histo" u 2 t "Red" w histograms, "" u 3 t "Green" w histograms, "" u 4 t "Blue" w histograms, 22 title ""
(taken from Philip K. Janert, Gnuplot in Action)
回答2:
The typical way to add horizontal and/or vertical lines is with an arrow
set arrow from x1,y1 to x2,y2 nohead linestyle ...
For a horizontal line, y1 and y2 will be the same. From your question, I'm a little unsure what you mean by "at 22", but I'm guessing you mean that you want to plot the line y=22 on top of your histogram. If that's the case, try this (before your plot command).
set arrow from graph 0,first 22 to graph 1,first 22 nohead lc rgb "#000000" front
来源：https://stackoverflow.com/questions/13497160/add-horizontal-line-histogram-gnuplot