📄 adamsbmacc.m
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%% Author: epokh
%% Website: www.epokh.org/drupy
%% This software is under GPL
function [T,Y,Theta]=Adamsbm(t0,tmax,n,y_inn,ar,al,vr,vl,b,theta0,XoY)
if(XoY=='y')
f='(A*t+B)*sin(C*t.^2+D*t+theta0)';
else
f='(A*t+B)*cos(C*t.^2+D*t+theta0)';
end
h=(tmax-t0)/n;
[l,m]=size(y_inn);
v=zeros(1,m);
T=[t0:h:t0+n*h]';
Y=y_inn;
r=4;
Theta=[theta0];
for i=1:r
vr=ar*i+vr;
vl=al*i+vl;
A=(ar+al)/2;
B=(vr+vl)/2;
C=(ar-al)/(2*b);
D=(vr-vl)/b;
theta=C*i^2+D*i+theta0;
Theta=[Theta;theta];
t=T(i);y=Y(i,:);
for j=1:m
fun(i,j)=eval(f(j,:));
end
end
fun=[fun;v];
coef1=[-9 37 -59 55 0]/24;
coef2=[0 1 -5 19 9]/24;
for i=r:n
vr=ar*i+vr;
vl=al*i+vl;
A=(ar+al)/2;
B=(vr+vl)/2;
C=(ar-al)/(2*b);
D=(vr-vl)/b;
theta=C*i^2+D*i+theta0;
Theta=[Theta;theta];
p=Y(i,:)+h*coef1*fun; %predictor
t=T(i+1);y=p; %evaluation
for j=1:m
fun(r+1,j)=eval(f(j,:));
end
Y(i+1,:)=Y(i,:)+h*coef2*fun; %corrector
y=Y(i+1,:); %evaluation
for j=1:m
fun(r+1,j)=eval(f(j,:));
end
fun=[fun(2,:);fun(3,:);fun(4,:);fun(5,:);v];
end
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