How to produce dependable dual y-axis?

Question

I have this dataset:

x-axis	y-axis	y2-axis
15	9.585	88.38
45	9.4185	86.85
60	9.2655	85.44

I want to produce plot that two different y-axis in gnuplot, which is dependable each other
But, I troubled to adjust the second y-axis to the first one As you can see from the graph and dataset, the value of each points didn't exactly same from the dataset, it's just like the y2-axis just plotted there, without even adjusted to the values in dataset.
Is it possible to produce such graph?

Here's my code I worked before:

set xrange [5:70]
set yrange [9.1:9.7]
set y2range [85:89]
unset key

set xtics 15 font ",18" nomirror
set xlabel "x-axis" font ",24"
set xlabel offset 0,-.5
set ytics .2 font ",18" nomirror 
set ylabel "y-axis" font ",24"
set ylabel offset -1.5
set y2tics font ",18" 
set y2label "y2-axis" font ",24"

plot "Dataset.txt" with linespoints ls 1

Answer 1

Please check help link. You can define a function (and the inverse of it) if you want to link axes.

Syntax:

  set link {x2 | y2} {via <expression1> inverse <expression2>}
  unset link

The set link command establishes a mapping between the x and x2 axes, or the y and y2 axes. maps primary axis coordinates onto the secondary axis. maps secondary axis coordinates onto the primary axis.

From your numbers I guess that the relation between your y1-axis and y2-axis is simply a factor of 9.221.

Script:

### linked y-axes
reset session

$Data <<EOD
x-axis  y-axis  y2-axis
15      9.585   88.38
45      9.4185  86.85
60      9.2655  85.44
EOD

c = 9.221

set xlabel "x axis"
set xrange [5:70]

set ylabel "y1 axis"
set ytics 0.1 nomirror

set link y2 via y*c inverse y/c
set y2label "y2 axis"
set y2tics 0.5

plot $Data u 1:2 w lp pt 7 lc "red"
### end of script

Result: