src/test/poiseuille.plot

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    ftitle(a,b) = sprintf("%.0f/x^{%4.2f}", exp(a), -b)
    f(x)=a+b*x
    fit f(x) 'log' u (log($1)):(log($4)) via a,b
    f2(x)=a2+b2*x
    fit f2(x) 'log' u (log($1)):(log($2)) via a2,b2
    set xlabel 'Resolution'
    set ylabel 'Error'
    set logscale
    set xrange [4:128]
    set cbrange [1:2]
    set xtics 4,2,128
    set grid ytics
    set yrange [1e-5:]
    plot 'log' u 1:4 t 'max', exp(f(log(x))) t ftitle(a,b), \
         'log' u 1:2 t 'norm1', exp(f2(log(x))) t ftitle(a2,b2)