grepg [FEATURE]: provide option to select plot axis range

src/green/grepg/grepg.f

@@ -657,10 +657,23 @@ c option -f
       fourierfile=optarg(50)
 c option -st
       adaptivetimescaling=optset(51)
+      read(optarg(52), *, err=99, end=98) xlbound,xubound
+      read(optarg(53), *, err=99, end=98) ylbound,yubound
 
 c      print *,subtitlestring
 c      print *,optarg(45)
 c 
+c ----------------------------------------------------------------------
+c check parameter consistency
+      if (xlbound.ge.xubound) then
+        stop 'ERROR: parameters given by -Xb must be l<u'
+      endif
+c 
+      if (ylbound.ge.yubound) then
+        stop 'ERROR: parameters given by -Yb must be l<u'
+      endif
+c ----------------------------------------------------------------------
+c 
 c covariances
       if (replot) implot=.false.
       if (phasecolor) phaseswitch=.false.
@@ -696,26 +709,43 @@ c report
         df=(om(2)-om(1))*1.e3
         minf=om(1)*1.e3
         maxf=minf+(nfreq-1)*df
+        pminf=max(xlbound,minf)
+        pmaxf=min(xubound,maxf)
         print *,'test slowness range: ',minf,'s/km - ',maxf,
      &          's/km du=',df,'s/km'
+        print *,'plot range: ',pminf,'s/km - ',pmaxf,'s/km'
       else
         df=(om(2)-om(1))/pi2
         minf=om(1)/pi2
         maxf=minf+(nfreq-1)*df
+        pminf=max(xlbound,minf)
+        pmaxf=min(xubound,maxf)
         print *,'frequency range: ',minf,'Hz - ',maxf,'Hz   df=',df,'Hz'
+        print *,'plot range: ',pminf,'Hz - ',pmaxf,'Hz'
       endif
       du=(slo(2)-slo(1))*1.e3
       mins=slo(1)*1.e3
       maxs=mins+du*(nslo-1)
+      pmins=max(ylbound,mins)
+      pmaxs=min(yubound,maxs)
       if (isgabor) then
         print *,' time range: ',mins,'s - ',maxs,'s   dt=',du,'s'
+        print *,' plot range: ',pmins,'s - ',pmaxs,'s'
       elseif (iskspec) then
         print *,' wavenumber range: ',mins,'1/km - ',maxs,
-     &    '1/km   dk=',du,'1/km'
+     &    '1/km   du=',du,'1/km'
+        print *,' plot range: ',pmins,'1/km - ',pmaxs,'1/km'
       else
         print *,' slowness range: ',mins,'s/km - ',maxs,
      &    's/km   du=',du,'s/km'
+        print *,' plot range: ',pmins,'s/km - ',pmaxs,'s/km'
       endif
+c 
+      if (pmaxf.le.pminf) 
+     &  stop 'ERROR: plot range is empty; check parameters for -Xb'
+      if (pmaxs.le.pmins) 
+     &  stop 'ERROR: plot range is empty; check parameters for -Yb'
+c 
       print *,' '
 c----------------------------------------------------------------------
 c initialize
@@ -1209,7 +1239,7 @@ c
 c plot box and box title and labels
 c ---------------------------------
 c
-      call pgenv(minf,maxf,mins,maxs,0,-2)
+      call pgenv(pminf,pmaxf,pmins,pmaxs,0,-2)
       call pgqvp(0,pg_vpl,pg_vpr,pg_vpb,pg_vpt)
       pg_vpr=1.-(1.-pg_vpr)*par_wedgeheight
       call pgsvp(pg_vpl,pg_vpr,pg_vpb,pg_vpt)

src/green/grepg/grepg_para.inc

@@ -46,8 +46,11 @@ c
 c 
 c original parameters
       real mins, minf, maxs, maxf
+c plot range parameters
+      real pmins, pminf, pmaxs, pmaxf
 c 
-      common /grepg_mainpara/ mins, maxs, minf, maxf
+      common /grepg_mainpara/ mins, maxs, minf, maxf,
+     &                        pmins, pmaxs, pminf, pmaxf
 c 
 c define normalizing taper
       real norm_center, norm_width