1 files changed, 5 insertions, 0 deletions
diff --git a/GradeBook_lib.tcl b/GradeBook_lib.tcl
index 21b590e..000bdfe 100755
--- a/GradeBook_lib.tcl
+++ b/GradeBook_lib.tcl
@@ -2307,6 +2307,11 @@ proc data2txtPlot { data } {
 	foreach x $data {
 	  # funky 1.1 are needed to convert it to floats
 		set cnt [expr { round((1.0*$x-$minVal)/(1.1*$diffVal)*(1.1*($barsNum-1.0))) }]
+
+		# safety check on counter value
+		set cnt [expr {min($cnt, ($barsNum-1))}]
+		set cnt [expr {max($cnt, 0)}]
+
 		set bar [lrange $chars $cnt $cnt]
 		lappend strPlot $bar
 	}