control of a script

hi! I wrote this script but i'm not sure if the response can be true, what do you think about it?

clc
clear all
dt=0.4;
[t,a]=ode45(@Law,[0 0+dt],[0;0;0;0]);

where

function [ da ] = Law( t,a )
[Ks,cs,I,m,g,L,K0,Kc,Icw,c0,cc,T0,r,alfa,mcw,lc,lcw,ls]=deal(1.0e+07,133.58,7.3777e-04,0.105795,9.78,0.0709444,0.37,1.0e+06,2.7195e-05,9.3e-05,24.22,0.12,0.028284,pi/4,0.11887,0.12,0.010528,0.09);
A=400;
w=1257;
h=0.003;
yl=lc*tan(a(1));
dyl=lc*a(3)/(cos(a(1)))^2;
yc=r*(sin(alfa)-sin(alfa-a(1)));
dyc=r*a(4)*cos(alfa-a(2));
yu=lc*tan(a(1))+h/cos(a(1));
dyu=((lc+h*sin(a(1)))*a(3))/(cos(a(1)))^2;
%value of Fs
if a(1)>=0
    Fs=0;
else   
    Fs=-Ks*ls*a(1)-cs*ls*a(3);
end
%value of R
if yc<yl
    R=lc/cos(a(1));
elseif (yl<yc) && (yc<yu) 
    R=0;
elseif (yl==yc) && (yc==yu) 
    R=0;
elseif (yl==yc) && (yc<yu)
    R=0;
elseif (yl<yc) && (yc==yu)
    R=0;
elseif yc>yu
    R=lc/cos(a(1))+h*tan(a(1));
end
%value of Fr
if yc<yl
    Fr=Kc*(yl-yc)*cos(a(1))+cc*(dyl-dyc)*cos(a(1))-(yl-yc)*a(3)*sin(a(1));
elseif (yl<yc) && (yc<yu)
    Fr=0;
elseif (yl==yc) && (yc==yu)
    Fr=0;
elseif (yl==yc) && (yc<yu)
    Fr=0;
elseif (yl<yc) && (yc==yu)
    Fr=0;
elseif yc>yu
    Fr=Kc*(yu-yc)*cos(a(1))+cc*(dyu-dyc)*cos(a(1))-(yu-yc)*a(3)*sin(a(1));
end
%law
da=[a(3);a(4);Fs*ls/I-(R*Fr)/(I)-(m*g*A*L*sin(w*t)*cos(a(1)))/I;-K0*a(2)/Icw-c0*a(4)/Icw-T0/Icw+Fr*r*cos(a(1))*cos(alfa-a(2))/Icw+(mcw*g*lcw*(A*sin(w*t)*cos(a(2))+sin(a(2))))/Icw];

end

thanks in advance!

Answer 1

[Walter Roberson]

When you have two values that are computed through different paths and the two values mathematically should represent the same quantities, then often the two values will not compare equal with == . This is due to floating point round off. For example, ((10/3)*3) might not compare exactly equal to 10.

[Guido De Angelis]

thank you so much for your disponibility, except this problem do you think that the script and the function can be correct?