Gnuplot 简单使用

http://www.duke.edu/~hpgavin/gnuplot.html

 

基本语法：

 

plot and splot are the primary commands in Gnuplot. They plotfunctions and data in many many ways. plot is used to plot 2-d functions and data, while splot plots 3-d surfaces and data.

Syntax:



       plot {[ranges]}



            {[function] | {"[datafile]" {datafile-modifiers}}}



            {axes [axes] } { [title-spec] } {with [style] }



            {, {definitions,} [function] ...}







几个简单的例子：








For example, try:



gnuplot>  plot sin(x)/x   

gnuplot>  splot sin(x*y/20)

gnuplot>  plot sin(x) title 'Sine Function', tan(x) title 'Tangent'

 

从文件中读取数据，并作图：

Discrete data contained in a file can be displayed by specifying the nameof the data file (enclosed in quotes) on the plot or splot command line. Data files should have the data arranged in columns ofnumbers. Columns should be separated by white space (tabs or spaces)only, (no commas). Lines beginning with a # character are treatedas comments and are ignored by Gnuplot. A blank line in the data fileresults in a break in the line connecting data points.

For example your data file, force.dat , might look like:

以空白字符作为行列分割， 空行表示数据分段

      # This file is called   force.dat



      # Force-Deflection data for a beam and a bar



      # Deflection    Col-Force       Beam-Force 



      0.000              0              0    



      0.001            104             51



      0.002            202            101



      0.003            298            148



      0.0031           290            149



      0.004            289            201



      0.0041           291            209



      0.005            310            250



      0.010            311            260



      0.020            280            240

You can display your data by typing:

      gnuplot>  plot  "force.dat" using 1:2 title 'Column', /



                      "force.dat" using 1:3 title 'Beam'

Do not type blank space after the line continuation character, "/" .

Your data may be in multiple data files. In this case you may makeyour plot by using a command like:

也可以从不同的文件中读取数据

      gnuplot>  plot  "fileA.dat" using 1:2 title 'data A', /



                      "fileB.dat" using 1:3 title 'data B'

For information on plotting 3-D data, type: 关于3d请看帮助

      gnuplot>  help splot datafile

改变图片的风格：
















后面跟with来改变做出的图形样式













      gnuplot> plot "force.dat" using 1:2 title 'Column' with lines


, /



                    "force.dat" u 1:3 t 'Beam' w linespoints










Plots may be displayed in one of eight styles: 



lines, points, linespoints, impulses, dots, steps, fsteps, histeps,



errorbars, xerrorbars, yerrorbars, xyerrorbars, boxes, boxerrorbars,



boxxyerrorbars, financebars, candlesticks or vector











设置全局的格式：













使用set





命令来设置样式，用replot





命令来显示改变情况







      Create a title:                  > set title "Force-Deflection Data" 



      Put a label on the x-axis:       > set xlabel "Deflection (meters)"



      Put a label on the y-axis:       > set ylabel "Force (kN)"



      Change the x-axis range:         > set xrange [0.001:0.005]



      Change the y-axis range:         > set yrange [20:500]



      Have Gnuplot determine ranges:   > set autoscale



      Move the key:                    > set key 0.01,100



      Delete the key:                  > unset key



      Put a label on the plot:         > set label "yield point" at 0.003, 260 



      Remove all labels:               > unset label



      Plot using log-axes:             > set logscale



      Plot using log-axes on y-axis:   > unset logscale; set logscale y 



      Change the tic-marks:            > set xtics (0.002,0.004,0.006,0.008)



      Return to the default tics:      > unset xtics; set xtics auto







一个图片上，画多个图






      set multiplot;                          # get into multiplot mode

      set size 1,0.5;  

      set origin 0.0,0.5;   plot sin(x); 

      set origin 0.0,0.0;   plot cos(x)

      unset multiplot                         # exit multiplot mode





输出文件:

set terminal jpeg

set output "your_output_file"

plot sin(x)/x

这样输出的文件就是jpeg的格式了。