diff --git a/controls/MATLAB/momentOfInertia/J_calc_bifilar.m b/controls/MATLAB/momentOfInertia/J_calc_bifilar.m
index 9f52a69ec50752c0c2b2b644f1a5b373ccc74bcb..0e7945bfff9acae2a5dfcefe2c7f0278ccbca208 100644
--- a/controls/MATLAB/momentOfInertia/J_calc_bifilar.m
+++ b/controls/MATLAB/momentOfInertia/J_calc_bifilar.m
@@ -1,6 +1,14 @@
 function  J  = J_calc_bifilar( m , g, D, L, t, n , varargin)
-%UNTITLED Summary of this function goes here
-%   Detailed explanation goes here
+% J  = J_calc_bifilar( m , g, D, L, t, n)
+% J  = J_calc_bifilar( m , g, D, L, t, n , mode_option)
+% 
+% m , D , L , t , and n are vectors containing the mass, distance between
+% strings, legnth of strings, time, and cycles of a set of tests. g is the
+% acceleration of gravity you want to use. 
+% 
+% mode_option is an optional input which will specify how to calculate J: 
+% mode_option = 0 will use averageing of the trials (default) 
+% mode_option = 1 will use least squares of the whole data set 
 
 average_strings = {'average','mean','ave'}; 
 least_squares_strings = {'least squares','ls'}; 
@@ -30,7 +38,5 @@ if mode == 1 %least squares
     J = (16*pi^2*L./(m*g.*D.^2))\(t./n).^2 ; 
 end
 
-
-
 end