diff --git a/plot.sh b/plot.sh
index 2718b9a..86b53cc 100755
--- a/plot.sh
+++ b/plot.sh
@@ -2,14 +2,20 @@
 
 #           THIS IS A KLUDGE 
 
+nbsamp=3000	# nombre d'echantillon 
+
+if [ $# -eq 1 ]; then
+	nbsamp=$1
+fi
 
 DATAFILE="serial/foo.dat"
 IMAGE="graphe.png"
 TMPFILE="/dev/shm/tmpdata"
 
+echo $nbsamp
 wc -l ${DATAFILE}
 
-tail -2500 < ${DATAFILE} > ${TMPFILE}
+tail -3000 < ${DATAFILE} > ${TMPFILE}
 
 gnuplot << __EOC__
 set term png 	size 1600,800