如何修改Gnuplot脚本使图例置于绘图外且不压缩绘图？

问题说明 #

使用Gnuplot生成SVG格式绘图时，设置图例（key）为外置（outside）后，主绘图区域会被压缩。由于SVG是矢量文件无法直接查看边距参数，常规调整方法无效，需要针对性修改脚本。

原始数据 #

"potential" "Bare" "1/2ML OH Fe" "1/2ML OH Cu" "1ML OH" "1ML OH Fe" "1ML OH Cu" "3/2ML OH Fe" "3/2ML OH Cu" "2ML OH" "0-2"
0.00           0         0.949         0          0           0          0            2.685         4.636     4.511
1.23           0        -0.281         0          0           0          0           -1.005        -0.454    -0.409


"potential" "Bare" "1/2ML OH Fe" "1/2ML OH Cu" "1ML OH" "1ML OH Fe" "1ML OH Cu" "3/2ML OH Fe" "3/2ML OH Cu" "2ML OH" "0-6"
0.00           0         0.267         0          0           0          0            2.632         3.960     4.710
1.23           0        -0.533         0          0           0          0           -1.058         0.370    -0.200


"potential" "Bare" "1/2ML OH Fe" "1/2ML OH Cu" "1ML OH" "1ML OH Fe" "1ML OH Cu" "3/2ML OH Fe" "3/2ML OH Cu" "2ML OH" "1-1"
0.00           0        -0.295         0          0           0          0            0.498         0.503     2.403
1.23           0        -1.605         0          0           0          0           -2.892        -2.087    -2.517

原始脚本 #

#!/usr/local/Cellar/gnuplot/5.4.4/bin/gnuplot
### Batch create SVG files from multiple subblocks

FILE = "total.dat"

     set term svg font "{/:Bold}Sans,25"
     #set term qt font "Sans,21"
     set border 15 front linecolor rgb "black"  linewidth 3.000 dashtype solid
     #set key noautotitle samplen 2
     set format x "%.1f"
     #set nokey
     set key top right
     set key outside
     set key font "{/:Bold,15}"
     #set key at 2.3,2,0
     set xrange [0:1.23]
     set yrange [-2:2]
     set xlabel "U (V vs. RHE)"
     set xlabel  offset character 0,0.6,0 font "{/:Bold},23"
     set ylabel "{/Symbol D}G (eV)"
     set ylabel  offset character 1.0, 0, 0 font "{/:Bold},26"
     set xtics nomirror font "{/:Bold},24"
     set ytics nomirror font "{/:Bold},24"
     set title noenhanced
     myFileOut(s) = sprintf("%s.svg",s)

     do for [i=0:2] {
         stats FILE index i every ::::0 u (s=strcol(11),0) nooutput
         set output myFileOut(s)

         plot FILE index i u 1:2 w l lw 3 title columnheader(2), \
         "" index i u 1:3 w l lw 3 title columnheader(3), \
         "" index i u 1:4 w l lw 3 title columnheader(4), \
         "" index i u 1:5 w l lw 3 title columnheader(5), \
         "" index i u 1:6 w l lw 3 title columnheader(6), \
         "" index i u 1:7 w l lw 3 title columnheader(7), \
         "" index i u 1:8 w l lw 3 title columnheader(8), \
         "" index i u 1:9 w l lw 3 title columnheader(9), \
         "" index i u 1:10 w l lw 3 lc rgb "pink" title columnheader(10)

}
 set output

修改后的脚本 #

#!/usr/local/Cellar/gnuplot/5.4.4/bin/gnuplot
### Batch create SVG files from multiple subblocks

FILE = "total.dat"

# 固定SVG画布尺寸并设置字体
set term svg font "{/:Bold}Sans,25" size 1000,700
#set term qt font "Sans,21"
set border 15 front linecolor rgb "black" linewidth 3.000 dashtype solid
#set key noautotitle samplen 2
set format x "%.1f"
#set nokey

# 手动设置边距：给右侧图例预留空间
set lmargin at screen 0.1    # 左侧边距占画布10%
set rmargin at screen 0.75   # 右侧边距截止到画布75%，剩下25%给图例
set tmargin at screen 0.95   # 顶部边距
set bmargin at screen 0.15   # 底部边距

# 设置图例位置：右上角外置，合并参数避免冲突
set key top right outside font "{/:Bold,15}"
#set key at 2.3,2,0
set xrange [0:1.23]
set yrange [-2:2]
set xlabel "U (V vs. RHE)"
set xlabel offset character 0,0.6,0 font "{/:Bold},23"
set ylabel "{/Symbol D}G (eV)"
set ylabel offset character 1.0, 0, 0 font "{/:Bold},26"
set xtics nomirror font "{/:Bold},24"
set ytics nomirror font "{/:Bold},24"
set title noenhanced
myFileOut(s) = sprintf("%s.svg",s)

do for [i=0:2] {
    stats FILE index i every ::::0 u (s=strcol(11),0) nooutput
    set output myFileOut(s)

    plot FILE index i u 1:2 w l lw 3 title columnheader(2), \
    "" index i u 1:3 w l lw 3 title columnheader(3), \
    "" index i u 1:4 w l lw 3 title columnheader(4), \
    "" index i u 1:5 w l lw 3 title columnheader(5), \
    "" index i u 1:6 w l lw 3 title columnheader(6), \
    "" index i u 1:7 w l lw 3 title columnheader(7), \
    "" index i u 1:8 w l lw 3 title columnheader(8), \
    "" index i u 1:9 w l lw 3 title columnheader(9), \
    "" index i u 1:10 w l lw 3 lc rgb "pink" title columnheader(10)

}
set output

关键改动说明 #

• 固定SVG画布尺寸：通过size 1000,700指定画布宽高，避免Gnuplot自动调整画布大小导致绘图区域压缩
• 手动设置屏幕边距：用set *margin at screen命令直接基于画布比例分配空间，确保主绘图区域和图例各占固定比例，互不挤压
• 合并图例参数：将set key top right、set key outside、set key font合并为一行，避免参数冲突，确保图例定位准确

内容的提问来源于stack exchange，提问作者Courtney Brea