function [Magx1,Magx2] = findmag(x1,x2,u)
%
% utility to find the magnitude from freq resp data:
%
% [Magx1,Magx2] = findmag(x1,x2,u)
%
% Determines the Bode magnitude ratio from a set of frequency response data
% x1 = response of first mass (cm)
% x2 = response of second mass (cm)
% u = amplitude of input
%
% Assumes that the data set is 5000 samples long
% (Equivalent to 20s of ECP data under RTW)
% Find the means of the steady-state signals.
p1 = polyfit(0:1000,x1(4000:5000)',1);
p2 = polyfit(0:1000,x2(4000:5000)',1);
% Subtract the mean from the steady state signals.
Enc1cm = x1(4000:5000) - (polyval(p1,0:1000))';
Enc4cm = x2(4000:5000) - (polyval(p2,0:1000))';
% Compute the magnitude ratios.
Magx1 = max(Enc1cm)/u;
Magx2 = max(Enc4cm)/u;