如何在Gnuplot中为增量定义的等高线添加离散临界等高线

我需要为通过set cntrparam levels increment命令定义的等高线集合添加一条临界等高线。原本打算用set cntrparam levels discrete实现添加，但该命令会覆盖原有等高线，不符合需求。我编写了Windows环境下的Gnuplot脚本尝试修改，运行后出现**"All points of colorbox value undefined"**错误提示，相关脚本及数据文件如下：

问题脚本 #

reset session

set grid x,y front

set xrange noextend
set yrange noextend

stats "datos0.txt" u 3 nooutput
set zrange [STATS_min:STATS_max]
set dgrid3d 900,900 qnorm 9 
set contour
set view 0,0,1
v = 7; w = 0.1 * int((STATS_max-STATS_min-0.2)*10./(v-1.))

# MODIFICATION: THE NEXT 3 LINES ARE REPLACED BY THE FOLLOWING 11 LINES
#set cntrparam levels incremental STATS_min+0.1,w,STATS_max-0.1
## IF THE FOLLOWING 'IF' SENTENCE IS TRUE, THE PRECEEDING CONTOUR LEVELS ARE ALL REPLACED BY JUST ONE DISCRETE LEVEL 
#if ((((STATS_max-STATS_min-0.2) - int(STATS_max-STATS_min-0.2))/w) >= 0.5) { set cntrparam levels discrete STATS_max-0.1}

# create level string and sort it by value
   set table $Temp
       set samples v
       plot '+' u (STATS_min+0.1+$0*w) w table
   if ((((STATS_max-STATS_min-0.2) - int(STATS_max-STATS_min-0.2))/w) >= 0.5) { plot '+' every ::::0 u (STATS_max-0.1) w table}
  
   set table $Levels
       plot $Temp u 1:0 smooth freq   # sort levels
   unset table
   myLevels = ''
   stats $Levels u (myLevels = myLevels.($0==0?'':', ').strcol(1)) nooutput
   set cntrparam level discrete @myLevels

        set palette rgbformulae 33,13,10   
        set cbrange[STATS_min:STATS_max]
        set cbtics 0.2
        set colorbox vertical user origin 0.93,0.38 size .02,.585

# THESE 3 LINES, THOUGH USELESS, ARE NECESSARY TO AVOID AN 'undefined value' ERROR MESSAGE WHEN EXECUTING THE LAST 3 LINES OF THE SCRIPT 
set table $qq
    splot "datos0.txt"
unset table

set cntrlabel format "{/:Bold %.1f}" font "Times-New Roman, 10" onecolor
  set lmargin
  set origin -0.373,-0.375
 set size 1.735,1.74  #  VALE 1.034 per la umid. e 1.023 per il vento

# Use a coarser grid when generating labels  
# use a dummy definition g = $smallgrid() to force a single execution of a function that resets the grid parameters
function $smallgrid() << EOF
    set dgrid3d 95,95 qnorm 9
EOF

set pm3d explicit
splot "datos0.txt" with pm3d, \
      '' with lines lw 1 lc "black" nosurface, \
      g=$smallgrid() '' with labels pointnumber 1

数据文件（datos0.txt） #

0   66  0.2
 0   69  0.3
 0   70  0.3
 0   72  0.7
 0   74  0.1
 0   74.1    0.1
 0   79  0.3
 0   80  0.2
 0   81  0.3
 0.1     61  -0.1
 0.1     70  0.3
 0.1     74  0.7
 0.1     75  0.8
 0.1     75.1    0.3
 0.1     78  0.2
 0.2     73  0.4
 0.2     75  0.5
 0.3     59  0.5
 0.3     74  0.4
 0.3     75  0.1
 0.3     76  0.6
 0.3     78  0.2
 0.4     71  0.3
 0.4     73  0.4
 0.4     74  0.6
 0.5     54  1.1
 0.5     69  0.2
 0.5     76  0.6
 0.5     84  0.3
 0.6     55  0.3
 0.6     67  0.3
 0.6     68  0.4
 0.6     76  0.4
 0.6     77  0.5
 0.6     79  0.2
 0.6     80  0.4
 0.7     68  0.2
 0.7     72  0.1
 0.7     73  0
 0.7     76  0.4
 0.7     76.1    0.4
 0.7     77  0.5
 0.7     77.1    0.3
 0.7     81  0.2
 0.8     46  1
 0.8     54  0.1
 0.8     63  0.5
 0.8     68  0.3
 0.8     73  -0.1
 0.8     74  0.3
 0.8     78  0.3
 0.8     81  0.3
 0.8     82  0.2
 0.9     50  0.8
 0.9     56  0.5
 0.9     60  1.2
 0.9     65  0.3
 0.9     70  0.7
 0.9     74  0.2
 0.9     79  0
 0.9     80  0.2
 0.9     80.1    0.1
 1   69  0.4
 1   76  0.5
 1   81  0.2
 1.1     54  0.3
 1.1     73  0.1
 1.1     76  0.3
 1.1     76.1    0.4
 1.1     81  0.2
 1.2     56  0
 1.2     75  0.3
 1.2     79  0.1
 1.3     68  0.3
 1.3     75  0.3
 1.3     82  0.3
 1.4     46  0.2
 1.4     66  0.7
 1.4     71  0.2
 1.4     78  0
 1.4     81  0.3
 1.4     81.1    0.4
 1.5     45  0.9
 1.5     60  1.3
 1.5     71  0.1
 1.5     76  0.1
 1.5     82  0.2
 1.5     82.1    0.2
 1.5     82.2    0.2
 1.5     84  0.2
 1.6     55  0.9
 1.6     57  1.4
 1.6     71  0
 1.6     81  0.1
 1.6     82  0.1
 1.6     83  0.1
 1.6     84  0.3
 1.7     62  0.3
 1.7     66  1
 1.7     75  0.4
 1.7     76  0.3
 1.7     78  0.3
 1.7     78.1    0.1
 1.7     80  0.1
 1.7     84  0.3
 1.8     56  0.3
 1.8     63  0.3
 1.8     67  0.6
 1.8     69  0.3
 1.8     77  0.1
 1.8     77.1    0.4
 1.8     78  0.3
 1.8     79  0.3
 1.8     84  0.2
 1.9     49  0.2
 1.9     53  0.3
 1.9     53.1    0.3
 1.9     54  0.2
 1.9     79  0.1
 1.9     82  0.3
 1.9     84  0.3
 2   60  1
 2   68  0.2
 2   73  0.5
 2   77  0.2
 2.1     45  1
 2.1     61  0.6
 2.1     66  0.4
 2.1     82  0.1
 2.2     61  0.1
 2.2     64  0.2
 2.3     64  0.5
 2.3     70  0.2
 2.3     76  0.1
 2.4     73  0.1
 2.5     53  0.2
 2.5     68  -0.1
 2.5     74  0.1
 2.5     79  0.1
 2.6     43  0.9
 2.6     65  0.8
 2.6     70  0.1
 2.8     61  0.4
 2.9     61  0.5
 3   54  0.4
 3.1     69  0.2
 3.2     57  0.3
 3.2     67  0.4
 3.5     65  1.1
 3.8     54  0.3
 3.8     60  0.2
 3.9     53  0.6
 3.9     65  0
 4.1     46  0.9
 4.1     48  0.8
 4.2     56  0.8
 4.3     43  1.1
 4.3     45  1.1
 4.6     44  1
 4.7     44  0.7
 4.7     46  0.9
 4.7     52  0.7
 5.5     44  0.9
 6.6     70  -0.5

脚本原本预期根据条件判断，输出单等高线标签或增量等高线标签两种结果，但修改后的方案出现上述报错。

内容的提问来源于stack exchange，提问作者ifffam