gnuplot

Created: 27 Dec 2024
Updated: 04 Oct 2025
gnuplot.svg
Figure 1: gnuplot's logo
home http://gnuplot.info/
faq http://gnuplot.info/faq/index.html
wiki https://en.wikipedia.org/wiki/Gnuplot
wiki https://en.wikibooks.org/wiki/Gnuplot
online https://hostcat.fhsu.edu/cdclark/static/apps/gnuplot/
source http://sf.net/p/gnuplot/gnuplot-main/

cli

$ gnuplot [x11 options] [options] [scriptfile ...]
$ gnuplot -p -e "plot '-'" < rawnumbers # opens qt window
$ GNUTERM=dumb gnuplot -e 'plot sin(x)'
Table 1: flags
  -e CMDS  
  -c FILE [ARG] runs script S with given args
–persist -p - keep window after plotting ends
–slow -s - wait for slow font init
–default -d - do NOT read ~/.gnuplot
Table 2: environment variables
GNUTERM terminal override
FIT_LOG name of the log file, default: fit.log

language

#!/usr/bin/gnuplot -persist
a = 7             # variable assignent
f(x,d) = d * x**2 # functions
g(x)   = x <= 0 ? sin(x) : NaN

functions

input data

  • space separated by default
  • putting 2 newlines one after another, separate different blocks/groups of data

commands

multiplot layout N,N  
  title S  
  offset N,N  
unset OPTION  
set OPTION [VALUE]  
with (l)ines[*], dots[.], lines(points)  
show variables  
stats FILENAME name S shows file field statistics
    later can be referenced
    eg: S_min_x

plot

[re]plot [XRANGE] [YRANGE] INPUT [PLOT_A OPTS],
         [XRANGE] [YRANGE] INPUT [PLOT_B OPTS]
INPUT reads from…
"file.txt" file contents
"/dev/stdin" standard input
"<CMD" CMD stdout
"" re-use last given input
  • every - p++:b++:pstart:bstart:pend:bend
    • N - every N data points
    • N:N - every N data points, in every other block
  • for [VAR = NSTART : NEND]
  • for [VAR in LVAR] # LVAR = "30 15 5"
  • using N:N+1:N+n
  • smooth
    • frequency - points with the same X-value are replaced with 1 point with Y-values sum
    • [bezier¦mcsplines]
  • title S (for legend box)
  • bins=N - total N number of bins (NOT SIZE) in graph http://gnuplot.info/docs_6.1/loc9125.html
  • binvalue=[avg¦sum] - how to group each bin, default: sum
  • index N
    • reference block N of data (aka separated by 2 \n)
    • blocks index start at 0
  • with
    • histograms
    • filledcurves
      • [f]ill[s]tyle pattern N
    • dots
    • points
      • pointsize N
    • lines
      • [d]ash[t]ype N¦S
      • [l]ine[t]ype N
      • [l]ine[s]tyle N
      • [l]ine[w]idth N
      • [l]ine[c]olor COLOR
    • linespoint

fit

  1. We come up with a function shape that "fits" our data.
    • the function has 2 types of variables
    • variables that depend on the input (eg: x)
    • variables that we want to find it's value and make "constants" (eg: a)
  2. We use fit command giving it:
    • the function in 1)
    • the input data
    • the fields using
    • the list of variables to find
f(x) = a*x + b
fit f(x) "" using 1:2 via a,b
Example output
gnuplot> fit f(x) "file.txt" using 3:2 via a,b
iter      chisq       delta/lim  lambda   a             b
   0 4.3014300000e+04   0.00e+00  9.71e+00    1.000000e+00   1.000000e+00
   1 7.0509078061e+03  -5.10e+05  9.71e-01    1.315008e+00   6.153986e+00
   2 3.9723792475e+03  -7.75e+04  9.71e-02    9.075167e-01   1.243513e+01
   3 3.9719144040e+03  -1.17e+01  9.71e-03    9.024370e-01   1.251326e+01
   4 3.9719144040e+03  -1.81e-07  9.71e-04    9.024364e-01   1.251327e+01
iter      chisq       delta/lim  lambda   a             b

After 4 iterations the fit converged.
final sum of squares of residuals : 3971.91
rel. change during last iteration : -1.81067e-12

degrees of freedom    (FIT_NDF)                        : 363
rms of residuals      (FIT_STDFIT) = sqrt(WSSR/ndf)    : 3.30786
variance of residuals (reduced chisquare) = WSSR/ndf   : 10.9419

Final set of parameters            Asymptotic Standard Error
=======================            ==========================
a               = 0.902436         +/- 0.02768      (3.067%)
b               = 12.5133          +/- 0.3791       (3.03%)

correlation matrix of the fit parameters:
                a      b
a               1.000
b              -0.890  1.000

other

  • imagesc - matrix/heatmap - 2d contour
  • splot - 3d surface
  • hist
  • scatter3 - 3d points

options (setteable)

general

Table 3: S "string", N=number, F=float, P[0.0-1.0]
     
table "FILENAME" save plot to file, unset it after
encoding utf8  
title S the
scale N  
output S saves into filepath, unset it after
monochrome _  
object [N] rectangle  
  [N] fillstyle  
size P,P size in multiplot
  square  
origin P,P position in multiplot, from left and bottom
pause N seconds to pause
reread - REMOVED in 6.0 reread input

general: file parsing

     
datafile separator S  
  separator tab  
  separator comma input separator (default: space)
decimalsign S "." or ","
samples N[,N] sampling frequency
[xyz]data time tells ? axis is a date/time
timecolumn N FMT INPUT format date on column N
timefmt FMT INPUT format date
format [x¦y] FMT OUTPUT format string, eg: %.2f

general: axis styling

Table 4: S ="string", N=number, F=float
border [N] pick axis lines (takes a bitsum)
  linecolor COL  
grid - axis grid
logscale [x¦y] [N] with step N
autoscale [[x¦y]fix] prevents autoextend of scale
xdata time tells ? axis is a date/time
format [x¦y] FMT OUTPUT format string
[xyz][2]range [N:N] axis range
[xyz][2]tics nomirror axis numbers
  rotate  
  START,STEP,END  
  (S N[,S N]) custom labels S at point N
  font ",20" set font size to 20
[xyz]tic rotate by N rotates tic labels
[xyz][2]label S axis label
  offset N[,N]  
  font ",20" set font size to 20
label N at X,Y S puts a label at X,Y position

general: splot

dgrid3d N,N ????
xyplane N Z value where xyplane is
ticslevel N " DEPRECATED
colorbox - color range box
pm3d border lw 1 surface with lines
isosamples N splot lines draw per xz axis
view X,Z 0-180 rotation around axis
contour base  
cntrparam levels auto 9  
  levels discrete 1, -1  
  levels incremental -2 .05 .2  
  first 10 sort  
hidden    
hidden3d - non translucent (disables sample)
    linestyle 1/2 for top/bottom
    aka "hidden line removal" 
splot f(x,y) with pm3d          # surface
splot f(x,y) lc pal        lw 2 # sets isolines color/thicc
set     lt 1 lc "seagreen" lw 3

palette

http://gnuplot.info/demo/pm3dcolors.html 

set palette gray
set palette rgb 7,5,15
set palette defined (0 0 0 0, 0.3 1 0 0, 0.6 "blue", 1 "#ffffff")
set palette defined (0 "blue", 0.5 "red", 1 "white")
set palette defined (0 "black", 0.5 "blue", 0.5 "red", 1 "white")
set palette cubehelix start 0 cycles -1. saturation 1
set palette cubehelix start 1.2 cycles -1 saturation 1
set palette cubehelix start pi/2 cycles -1 saturation 1
set palette cubehelix start pi/2 cycles -15 saturation 1

key

key [BLTR] position legend box
  [no]box enable/disable
  at graph F, F  
  width N  
  font S use ",14" to change size only
  at N,N  

style

style fill transparent  
    solid  
  solid F  
  noborder _  
  data lines sets default for plot with …
    histograms  
  line N can be later referenced on plot
  histogram gap N  
    cluster  
    clustered  
    rowstacked  
    columnstacked  
test_page.png
Figure 2: gnuplot "test" command output

term[inal]

  • gif [animate¦delay N¦loop N]
  • webp [animate¦delay N¦loop N]
  • png [size¦font]
  • pngcairo
  • wxt
  • xterm (xterm tektronix mode)
  • dumb (aka ascii)

snippets

  • stream - draw last 200 lines, ten times per second 

    while (1) {
  plot "< tail -200 plot.dat" using 1:2 with lines
  pause 0.1
}

  • background fullscreen rectangle 

    set object rectangle \
    from screen 0,0 to screen 1,1 \
    behind \
    fillcolor rgb '$background' \
    fillstyle solid \
    noborder

examples

tools

gotchas

  • by default wants space separated fields
  • sizes are given in pixels, can be undesired when exporting at large dimensions
  • plot field indexing starts at $1
  • poor compiler messages
  • different compiler messages when reading a script or from -e
  • no %a date format for input parsing
  • to read from stdin "-" might not work in plot (?
    • use /dev/stdin
  • you cannot plot fields from differents files/inputs against each other
  • on multiplot, sometimes a plot will silently fail (?