问题
How can I limit the autoscaling of gnuplot, so that, as example for the y-max, it is at least a certain value and it would autoscale up to fixed "limit"?
From looking at the documentation, I only see how to fix min-, or max- end of the axis, while the other is being scaled automatically.
About autoscaling on PDF page 93
回答1:
Since version 4.6 gnuplot offers a new syntax to specify upper and lower limits for the autoscaling. For your case you could use
set xrange [0:100 < * < 1000]
Quoting from the documentation:
The range in which autoscaling is being performed may be limited by a lower bound <lb> or an upper bound <ub> or both. The syntax is
{ <lb> < } * { < <ub> }
For example
0 < * < 200
sets <lb> = 0 and <ub> = 200.
That syntax can be applied to both the minimum or maximum value of set *range.
To autoscale xmin but keeping it positive, use
set xrange [0<*:]
To autoscale x but keep minimum range of 10 to 50:
set xrange [*<10:50<*]
See the documentation about set xrange for more information.
回答2:
I don't think it is possible, either you have autoscaling on no-, min- or max-, or both axis i.e.:
set yrange [FIXED_MIN : FIXED_MAX]
set yrange [ * : FIXED_MAX]
set yrange [FIXED_MIN : *]
set yrange [ * : ]
Respectively.
回答3:
In this case, you could filter the data and let gnuplot do it's normal auto-scaling:
set yrange [*:*]
plot 'mydatafile' u 1:(($2 >= YMIN && $2 <= YMAX) ? $2 : 1/0)
回答4:
Since people seem to be interested in this question, I'll add the way I solved this as an answer:
I made the minimum for the autoscaling by inserting a invisible marker in the beginning of the data. That cause the plot to always "show" it, even though it can not bee seen.
Then I implemented the maximum outside of gnuplot (propably could have been possible inside it as well, take a look at mgilson's answer), in a parser script that I have used to prepare the data for gnuplot.
Actually in the script I took all the "clipped out" values, added them to y=0, and made them red. That way I get a "warning", of values being too big to be sensible to graph. (My program monitors pings between two hosts, and there is no sense trying to graph 5s+ latencies => I mark it as connection broken)
来源：https://stackoverflow.com/questions/11269877/gnuplot-minimum-and-maximum-boundaries-for-autoscaling