Gnuplot:找到给定y的x值 [英] Gnuplot: find x value for given y

问题描述

我想完全这样做:

I want to do exactly this: https://tex.stackexchange.com/questions/165360/pgfplots-and-gnuplot-how-to-add-asymptote-a-xtick-that-isnt-a-number-and-can/165366#165366?newreg=53a345ba2c3f4f4fbf210af7872b1168 but in gnuplot (without the latex stuff). How can I do that?

这是我的plt文件:

reset
set xlabel "Distance [kpc]"
set ylabel "Velocity [km/s]"
unset key
set grid
f(x)=m*x+b
set xrange [0:10]
set yrange [10:]
set xtics
set xtics nomirror
set ytics nomirror
set logscale y
fit f(x) "vd.dat" u 1:2 via m, b
plot f(x) lw 2 lc rgb"black"
set term png
set output "~/uni/J2017+0603/J2017+0603_sim_pm_modified.png"
show output
plot f(x) lw 2 lc rgb"black"

这是输出: 绘制http://www.ifirn.de/inh/J2017+0603_sim_pm_modified.png

例如，我想知道哪个距离属于87km/s. 然后我用gnuplot在87km/s的水平线上绘制图形，然后垂直向下到x轴并显示结果.

And I want to know, for example, which distance belongs to 87km/s. And I wnat gnuplot to draw a horizontal line from 87km/s to graph, then vertical down to the x-axis and display the result.

推荐答案

该过程与您提供的链接中所述的过程相同:查找该函数的逆并添加结果.

The procedure is the same as described in the link you give: Find the inverse of the function and add the result.

您的函数的倒数是(f(x)-b)/m.要显示结果，请使用set arrow，使graph坐标系命中轴，并使用first获取实际交点的坐标.

The inverse of your function is (f(x)-b)/m. To display the result, use set arrow, with the graph coordinate system to hit the axes, and first to get the coordinates of the actual intersection.

要在轴上添加结果，请使用set xtics add和set ytics add.

To add the results on the axes, use set xtics add and set ytics add.

一个示例脚本(无配件):

An example script (without the fitting part):

reset
set xlabel "Distance (kpc)"
set ylabel "Velocity (km/s)"
set grid

m = 234; b = 1
f(x)=m*x+b
set xrange [0:10]
set yrange [10:]
set tics nomirror
set logscale y

set samples 1000
y = 2000.0

set arrow from graph 0, first y to first (y-b)/m,y nohead lt 3
set arrow from first (y-b)/m, y to first (y-b)/m, graph 0 nohead lt 3
set ytics add (sprintf("%.f", y) y)
set xtics add (sprintf("%.2f", (y-b)/m) (y-b)/m)
plot f(x) lw 2 lc rgb"black"

这篇关于Gnuplot:找到给定y的x值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！