diff --git a/include/plot.h b/include/plot.h
index 65832db..27a9b58 100644
--- a/include/plot.h
+++ b/include/plot.h
@@ -104,7 +104,7 @@ namespace ecolab
     bool displayRHSscale() const {return !penSide.empty() && miny1<maxy1;}
     bool displayLHSscale() const {return miny<maxy;}
     string axisLabel(double x, double scale, bool percent=false) const;
-
+    bool onlyMarkers() const; ///< return true if the only data is marker data
   public:
     Plot(): palette(paletteSz), msg(NULL), nxTicks(30), nyTicks(30), fontScale(1),
             offx(0), offy(0), logx(false), logy(false), 
diff --git a/src/plot.cc b/src/plot.cc
index 5ff0d90..9b432e6 100644
--- a/src/plot.cc
+++ b/src/plot.cc
@@ -294,6 +294,13 @@ namespace ecolab
     penSide[pen]=side;
   }
 
+  bool Plot::onlyMarkers() const
+  {
+    bool r=true;
+    for (size_t i=0; i<x.size(); ++i)
+      r &= x[i].empty() || (i<penSide.size() && penSide[i]==marker);
+    return r;
+  }
 
   void Plot::setMinMax()
   {
@@ -301,7 +308,7 @@ namespace ecolab
     msg=NULL;
     
     // calculate min/max
-    if (x.empty() || (!penSide.empty() && penSide[0]==marker))
+    if (onlyMarkers())
       {
         minx=logx? 0.1: -1;
         maxx=1;