gnuplot:如何为不同单位添加y2轴比例 [英] Gnuplot: how to add y2 axis scale for different units
问题描述
我正在从文件中绘制数据.数据点以公制为单位.我想在右边以标准单位显示第二个比例尺(y2).
I'm plotting data from a file. The data points are in metric units. I want to show a second scale on the right (y2) that's in standard units.
该文件表示随时间推移的火箭发动机推力.数据以牛顿为单位.我想在左边显示牛顿(自然发生)，而在右边显示磅力.转换是一个简单的因子(将N乘以0.2248得到lbf).
The file represents rocket motor thrust over time. The data are in Newtons. I want to show newtons on the left (this happens by itself, naturally) and pounds force on the right. The conversion is a simple factor (multiply N by 0.2248 to obtain lbf).
我可以设置y2tics，如果手动设置y2range，它们将显示在右侧.我不知道该怎么办，是将y2range自动设置为y1range *一个因数.
I can set y2tics and if I set y2range manually, they appear on the right. What I don't know how to do is set y2range automatically to y1range * a factor.
我最终的解决方案是绘制两次，一次在y1上以牛顿为单位，一次在y2上以磅为单位，然后使y2的图几乎不可见:
My eventual solution is to plot twice, once in Newtons on y1 and once in pounds on y2, and make the y2 plot almost invisible:
plot '-' using 1:($2*0.2248) with dots axes x1y2 lc rgb 'white' notitle, \
'' using 1:2 with lines lc rgb '<color>' title '<title>'
上面的解决方案通常会产生略有不同的y尺度:使用autoragne时，gnuplot将范围四舍五入，因此每个轴上的最高刻度是一个整数，当然，不同单位的舍入也不同.
The solution above often generates slightly different y scales: with autoragne, gnuplot rounds up the range so the top tick on each axis is a round number, and of course the rounding is different for different units.
最终，我最终得到了Python代码，该代码在每个图中都找到了最大推力值，然后我将yrange设置为该数字，并将y2range设置为该数字* 0.2248:
Ultimately I end up with Python code that finds the highest thrust value in each graph, then I explicitly set yrange to that number and y2range to that number * 0.2248:
f.write("set yrange [0:%s]; set y2range[0:%s]\n" % (peak_thrust, peak_thrust*NEWTON_LBF));
这是最终结果: http://www.lib.aero /hosted/motors/cesaroni_12-15-12.html (下面的示例图)
Here's the end result: http://www.lib.aero/hosted/motors/cesaroni_12-15-12.html (sample graph below)
推荐答案
在我看来，最简单的方法是简单地缩放数据:
It seems to me that the easiest way to do this is to simply scale the data:
set y2tics
plot sin(x) w lines, 5*sin(x) w lines axes x1y2
当然，您是从文件中绘制数据，因此看起来更像是:
Of course, you're plotting data from a file, so it would look something more like:
set y2tics
FACTOR=0.2248 #conversion factor from newtons to lbf
plot 'datafile' u 1:2 w lines, '' u 1:(FACTOR*$2) w lines
如果要显式设置yrange(可能需要这样做):
If you're setting the yrange explicitly (which you may need to do):
set yrange [ymin:ymax]
set y2range [ymin*FACTOR:ymax*FACTOR]
最后，如果您真的想依靠自动缩放，则需要做一些体操".
Finally, if you really want to rely on autoscaling, you're going to need to do some "gymnastics".
首先，设置一个虚拟端子，这样我们就可以plot而无需绘制图:
First, set a dummy terminal so we can plot without making a plot:
set term unknown
plot 'datafile' u 1:2 #collect information on our data
现在我们已经收集了有关数据的信息，我们可以设置真实的y2range
Now that we've collected information on the data, we can set our real y2range
FACTOR=0.2248
set y2range [FACTOR*GPVAL_Y_MIN : FACTOR*GPVAL_Y_MAX]
set y2tics nomirror
set ytics nomirror
现在设置终端并绘制数据:
Now set the terminal and plot the data:
set term ...
set output ...
plot 'datafile' u 1:2 w lines
这篇关于gnuplot:如何为不同单位添加y2轴比例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
