diff --git a/frontend/frontend.js b/frontend/frontend.js
index 57b5ee3..8d8e9ec 100644
--- a/frontend/frontend.js
+++ b/frontend/frontend.js
@@ -28,11 +28,10 @@ function fillTable (obj, dom) {
 
 function graphSpectralData (obj, dom) {
   // graphs the data from obj[0] into canvas at dom
-  var arr;
+  var arr = [];
   for (var i in ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'R', 'I', 'S', 'J', 'T', 'U', 'V', 'W', 'K', 'L']) {
     arr.push(obj[i]);
   }
-
   var chart = new Chart(dom, {
     type: 'line',
     data: {