# gnuplot
> 不要把軟體名稱打錯，正確寫法是 [gnuplot](http://www.gnuplot.info/)，開頭是 GNU，而非 GUN
> :notes: jserv

## 安裝

# Linux install command
sudo apt-get install -y gnuplot

## 檢查版本

$ gnuplot

        G N U P L O T
        Version 5.0 patchlevel 3    last modified 2016-02-21

        Copyright (C) 1986-1993, 1998, 2004, 2007-2016
        Thomas Williams, Colin Kelley and many others

        gnuplot home:     http://www.gnuplot.info
        faq, bugs, etc:   type "help FAQ"
        immediate help:   type "help"  (plot window: hit 'h')

Terminal type set to 'qt'
gnuplot>

## 測試畫圖

gnuplot 使用多種模式呈現圖

舉例來說上面出現`Terminal type set to 'qt'` 表示目前使用 qt 模式畫圖

但如果你沒安裝 qt 會顯示不出來

可以先用文字模式畫圖來測試 gnuplot 是否正常，先輸入 `set terminal` 檢查有哪些模式

gnuplot> set terminal

Available terminal types:
       cairolatex  LaTeX picture environment using graphicx package and Cairo backend
           canvas  HTML Canvas object
              cgm  Computer Graphics Metafile
          context  ConTeXt with MetaFun (for PDF documents)
            corel  EPS format for CorelDRAW
             dumb  ascii art for anything that prints text
              dxf  dxf-file for AutoCad (default size 120x80)
            eepic  EEPIC -- extended LaTeX picture environment
              emf  Enhanced Metafile format
            emtex  LaTeX picture environment with emTeX specials
         epscairo  eps terminal based on cairo
         epslatex  LaTeX picture environment using graphicx package
              fig  FIG graphics language for XFIG graphics editor
              gif  GIF images using libgd and TrueType fonts
             gpic  GPIC -- Produce graphs in groff using the gpic preprocessor
          hp2623A  HP2623A and maybe others
           hp2648  HP2648 and HP2647
             hpgl  HP7475 and relatives [number of pens] [eject]
           imagen  Imagen laser printer
             jpeg  JPEG images using libgd and TrueType fonts
            latex  LaTeX picture environment

可以看到 `dump` 就是用 ascii 模擬作圖

以下設定 `dump` 模式並畫一個範例圖，如果成功出現表示 gnuplot 正常

gnuplot> set terminal dumb
gnuplot> set xzeroaxis
gnuplot> set yzeroaxis
gnuplot> plot [-2:2] acos(1-abs(x))-pi,sqrt(1-(abs(x)-1)**2)
 2 ++-------+--------+--------+--------+-------+--------+--------+-------++
    +        +        +        +        +       + acos(1-abs(x))-pi ****** +
    |                                   :     sqrt(1-(abs(x)-1)**2) ###### |
  1 ++             ######               :              ######             ++
    |     #########      ##########     :    ##########      #########     |
    | ####                         #### :####                         #### |
    |#                                ####                                #|
  0 *+....................................................................+*
    |*                                  :                                 *|
    | ***                               :                              *** |
 -1 ++   *****                          :                         *****   ++
    |        *****                      :                     *****        |
    |             *****                 :                *****             |
    |                  *****            :           *****                  |
 -2 ++                      *****       :      *****                      ++
    |                            ****   :  ****                            |
    |                               *** :***                               |
 -3 ++                                ****                                ++
    +        +        +        +        +       +        +        +        +
    +--------+--------+--------+--------+-------+--------+--------+--------+
   -2      -1.5      -1      -0.5       0      0.5       1       1.5       2

現在改為 `qt` 模式測試

gnuplot> set terminal qt
Terminal type set to 'qt'
Options are '0 font "Sans,9"'
gnuplot> set xzeroaxis
gnuplot> set yzeroaxis
gnuplot> plot [-2:2] acos(1-abs(x))-pi,sqrt(1-(abs(x)-1)**2)
gnuplot>

會跳出畫好的圖案


## 參考文件
[gnuplot 官方網站](http://www.gnuplot.info/)

###### tags `Tool`