--- gnuplot/src/plot2d.c	2007-03-29 14:28:26.000000000 -0700
+++ gnuplot-cvs/src/plot2d.c	2007-04-08 17:51:07.000000000 -0700
@@ -1309,10 +1309,16 @@
         uses_axis[SECOND_X_AXIS] =
         uses_axis[SECOND_Y_AXIS] = 0;
 
+    /* Original Comment follows: */
     /* Reset first_plot. This is usually done at the end of this function.
      * If there is an error within this function, the memory is left allocated,
      * since we cannot call cp_free if the list is incomplete. Making sure that
      * the list structure is always valid requires some rewriting */
+    /* EAM Apr 2007 - but we need to keep the previous structures around in 
+     * order to be able to replot/zoom them without re-reading all the data.
+     */
+    if (first_plot)
+	cp_free(first_plot);
     first_plot = NULL;
 
     tp_ptr = &(first_plot);
@@ -2222,10 +2228,6 @@
             }
         }
     }   /* some_functions */
-    /* throw out all curve_points at end of list, that we don't need  */
-    cp_free(*tp_ptr);
-    *tp_ptr = NULL;
-
 
     /* if first_plot is NULL, we have no functions or data at all. This can
      * happen, if you type "plot x=5", since x=5 is a variable assignment */
@@ -2337,8 +2339,6 @@
 	update_gpval_variables(1);
     }
 
-    cp_free(first_plot);
-    first_plot = NULL;
 }                               /* eval_plots */