Index: /branches/eam_branches/ipp-20150112/Ohana/src/opihi/cmd.data/interpolate.c
===================================================================
--- /branches/eam_branches/ipp-20150112/Ohana/src/opihi/cmd.data/interpolate.c	(revision 37851)
+++ /branches/eam_branches/ipp-20150112/Ohana/src/opihi/cmd.data/interpolate.c	(revision 37852)
@@ -1,4 +1,5 @@
 # include "data.h"
 
+// XXX use 'threshold' to interpolate to a value
 int interpolate (int argc, char **argv) {
 
@@ -11,6 +12,7 @@
     gprint (GP_ERR, "USAGE: interpolate Xi Yi Xo Yo\n");
     gprint (GP_ERR, "  Xi Yi - sorted reference vectors\n");
-    gprint (GP_ERR, "  Xo    - output positions\n");
-    gprint (GP_ERR, "  Yo    - output values\n");
+    gprint (GP_ERR, "  Xo    - output positions (vector)\n");
+    gprint (GP_ERR, "  Yo    - output values (vector)\n");
+    gprint (GP_ERR, "  (use 'threshold' to interpolate to a value)\n");
     return (FALSE);
   }
@@ -18,4 +20,6 @@
   if ((xin  = SelectVector (argv[1],  OLDVECTOR, TRUE)) == NULL) return (FALSE);
   if ((yin  = SelectVector (argv[2],  OLDVECTOR, TRUE)) == NULL) return (FALSE);
+
+  // target positions are a vector
   if ((xout = SelectVector (argv[3],  OLDVECTOR, TRUE)) == NULL) return (FALSE);
   if ((yout = SelectVector (argv[4],  ANYVECTOR, TRUE)) == NULL) return (FALSE);