linux - 为什么我的命令对 gnuplot 不起作用？

Question

我有包含

的输入文件 test.dat

1 1
2 2
3 3 
4 4

我为 gnuplot 编写了脚本:

gnuplot <<EOF
set term png size 1000,1000;
set output "out.png";
set arrow from graph 0,1 to graph 0,1.1 filled
set arrow from graph 1,0 to graph 1.1,0 filled
set tmargin 5
set rmargin 20
set border 3
set tics nomirror
set grid
set xtics font "Verdana,14"
set ytics font "Verdana,14"  
set nokey
set style line 1 lt 1 lw 3 pt 3 linecolor rgb "black"
set ylabel "Efficiency, %" offset 2,0,0 font "Verdana,14"
set xlabel "Cores, N" offset 0,0,0 font "Verdana,14"
func1(x) = x / 2
func2(x) = x * 2
plot "test.dat" u (func1($1)):(func2($2)) ls 1 smooth csplines;
EOF

但是当您尝试启动它时出现错误:

gnuplot> plot "test.dat" u (func1()):(func2()) ls 1 smooth csplines;
         line 0: invalid expression 

Answer 1

美元符号被解释为开始一个 shell 变量。使用 column 代替:

gnuplot <<EOF
set term png size 1000,1000;
set output "out.png";
func1(x) = x / 2
func2(x) = x * 2
plot "test.dat" u (func1(column(1))):(func2(column(2))) ls 1 smooth csplines;
EOF