How do you increase the resolution of a contour plot in gnuplot? - gnuplot

I am using an analytical 2D function to make a contour plot. However, I do not get a smooth contour. (For example it should have been a circle but I get a oval shape.)
Here is the code snippet I am using:
splot f(x,y) t ''
set dgrid3d; set view 0,0
set cntrparam levels 10
set contour base
set nosurface
unset ztics
unset zlabel
set border 15
replot

Sounds like a matter of scale of the axes.
You can change the ranges of the axes using the xrange/yrange, etc
See, for example http://gnuplot.sourceforge.net/docs_4.2/node294.html

Related

Gnuplot: removing or moving tics at the border of graph with autoscaled tics

I'm trying to add an empty boundary around the data in an autoscaled graph without having tics in the empty boundary or at the border.
$ gnuplot -p -e "set offsets 0,0,0.1,0.1; plot sin(x)"
Desired result
Tics are gone at the y-axis border/in the empty boundary
set offsets 0,0,0.25,0.25
set yrange noextend
plot sin(x)
There is also the possibility to approach this quite differently, which may or may not be appropriate for your case.
set border 2
set ytics rangelimited
set xtics axis
set tics nomirror
set xzeroaxis
set offsets 0.,0.,.25,.25
plot sin(x)
Most likely you are looking for set autoscale noextend, check help noextend. You can give the offset also in graph coordinates to be independent of the actual y-scale, check help offsets.
Script:
### autoscale noextend
reset session
set autoscale noextend
set offsets 0,0, graph 0.1, graph 0.1
plot sin(x)
### end of script
Result:

Modifying the margin alignment in gnuplot in multiplot mode

I have created two plots in multiplot mode using epslatex as output terminal. The y axis labeling is different for both the plots.The first plot's y axis ranges from [0:45] and the second plot's y-axis ranges from [-5e-008 to 4e-007]. Due to the different widths of the y-axis labels, the width of the second plot is less than that of the first plot. I have tried the available scaling options but they do not work. Is it possible to edit the plot so that I can have the same width for both the plots irrespective of the y-axis range?
The problem you're experiencing can be reproduced by doing something like so:
set multiplot layout 2,1
plot sin(x)
plot 100000*sin(x)
The left margins are clearly not aligned. To fix this, you can try an explicit definition of where the margins lie:
set multiplot layout 2,1
set lmargin at screen 0.15
plot sin(x)
plot 100000*sin(x)
If your images are side by side, you can adjust the margins taking the appropriate offset into account:
set multiplot layout 1,2
set lmargin at screen 0.15
plot sin(x)
set lmargin at screen 0.5+0.15
plot 100000*sin(x)

One big and two small plots in multiplot gnuplot

I am trying to plot three different plots on the same canvas using the multiplot mode of gnuplot (version 5.0.1)
I want an arrangement of these plots in a particular way: final plot should show 2 rows with plot A in the upper row while plots B and C should appear in the lower row side-by-side as if for a lower row we had something like:
"set multiplot layout 1,2"
How can this be achieved?
Thanks in advance
you need to do the multiplot with the most "refined" grid, in this case 2x2 and then specify the size of each plot.
set multiplot layout 2,2
set size 1,0.5 # the first one has to be larger
plot sin(1*x)
set multiplot next # we want to skip the second (upright position)
set size 0.5,0.5 # the second and third have to be 0.5x0.5
plot sin(2*x)
plot sin(3*5)
unset multiplot
or as suggested here https://stackoverflow.com/a/15906085/2743307 it might be simpler to do it upwards (6 lines instead of 8!) but you have to specify the plots in opposite order:
set multiplot layout 2,2 upwards
plot sin(3*x)
plot sin(2*x)
set size 1,0.5
plot sin(1*x)
unset multiplot

Can Gnuplot put Two y-axis on the left hand side of a plot?

I'm trying to create a plot which has two independent y-axes on the left hand side, i.e. sharing the same x-axis. Is this possible in Gnuplot? I'm aware that it can be done with python for example.
You can just do the plot on gnuplot's standard x1y1 and x1y2 axes, and then add the extra axis with multiplot.
This example here is not perfect, but should give you an idea how to do it. As Christoph said, it's a bit fiddly:
set multiplot
set lmargin at scr 0.2
set bmargin at scr 0.1 # fix bottom margin
set y2range [0:20]
plot x, 2*x axes x1y2 # this is your actual plot
set lmargin at scr 0.1
set yrange [0:20] # set yrange to the same as y2 in the first plot
set border 2 # switch off all borders except the left
unset xtics # switch off the stray xtics
plot -1000 notitle # plot something outside of the y(2)range
unset multi

Gnuplot: Mix dgrid3d and point mode

I'm doing a 3d plot of values, and comparing them all against one single point. I'd like to have this single point clearly labelled in the graphs. Everything I've tried creates a plane that intersects this point due to dgrid3d I believe.
I think I can do this by overlapping two plots, but I feel like there must be an easier way.
Here is my script:
reset
set dgrid3d 10,10,10
set hidden3d
unset key
set xrange [0:550]
set yrange [0:550]
splot 'CAPS_data.dat' using 2:1:3 with linespoints
If you're comparing with only a few static points, you can add points via a labels:
set label 1 "" at X,Y,Z point
Otherwise, as you state, dgrid3d will turn that single point into a surface. The workaround for this sort of thing is to use a table and the plot your dgrid3d surface into the table. Then you can turn dgrid3d off and plot the surface with a different plotting style (e.g. pm3d).
set table "grid_data.dat"
set dgrid3d 100,100
splot "datafile.dat" u 1:2:3
unset table
unset dgrid3d
set term <whatever>
set output <whatever>
splot 'grid_data.dat' u 1:2:3 w pm3d,\
'point_data.dat' u 1:2:3 w points

Resources