Index: /issm/trunk-jpl/src/m/plot/plotmodel.py
===================================================================
--- /issm/trunk-jpl/src/m/plot/plotmodel.py	(revision 17616)
+++ /issm/trunk-jpl/src/m/plot/plotmodel.py	(revision 17617)
@@ -24,4 +24,7 @@
 	figurenumber=options.figurenumber
 	numberofplots=options.numberofplots
+
+	#get hold
+	hold=options.list[0].getfieldvalue('hold',False)
 
 	#if nlines and ncols specified, then bypass
@@ -52,6 +55,6 @@
 		#handling the 'visible' option will need some check on whether ipython is currently in interactive or non-interactive mode
 
-		#clear any previous plot window
-		p.clf()
+		if not hold:
+			p.clf()
 
 		#if figsize specified
Index: /issm/trunk-jpl/src/m/plot/processdata.py
===================================================================
--- /issm/trunk-jpl/src/m/plot/processdata.py	(revision 17616)
+++ /issm/trunk-jpl/src/m/plot/processdata.py	(revision 17617)
@@ -41,6 +41,8 @@
 	
 	#process NaN's if any
-	if options.exist('nan'):
-		data[npy.isnan(data)]=options.getfieldvalue('nan',0)
+	nanfill=options.getfieldvalue('nan',0)
+	if npy.any(npy.isnan(data)):
+		data[npy.isnan(data)]=nanfill
+		print "WARNING: nan's treated as zeros by default.  Change using pairoption 'nan',nan_fill_value in plotmodel call"
 
 	#non-patch processing