how with ode45 order we can solve a switching problem?

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azam ghamari
azam ghamari 2019-7-29
评论： Stephan 2019-8-1
Hi every one.
I want to write a code like this with ode45. how can I do it?
ode45(func)
func:
mode 1;
if x>=550
mode =2;
if mode=2 and x<=510
mode=1;
x'=f(x)= 0.1*x-50 mode =1
0.1*x-56 mode=2
I write this code, but gives me not correct output in figure
clc;
clear all;
close all;
deltat=10^-2;
x1(1)=510;
x11(1)=550;
for i=1:1000
x1(i+1)=(0.1*x1(i)-50)*deltat+x1(i);
y1(i)=x1(i);
if x1(i+1)>=550 && x1(i+1)==(0.1*x1(i)-50)*deltat+x1(i)
%return i;
x1(i+1)=(0.1*x1(i)-56)*deltat+x1(i);
y1(i)=x1(i);
elseif x1(i+1)<=510 && x1(i+1)==(0.1*x1(i)-56)*deltat+x1(i)
%return i;
x1(i+1)=(0.1*x1(i)-50)*deltat+x1(i);
y1(i)=x1(i);
end
end
figure(1)
plot(i,y1(i))
And what may I do to ruturn "i" as index when "x" reaches 550 or 510?
writing the above code "return i" it gives this error:
Error: File: ntest.m Line: 12 Column: 16
Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax
error. To construct matrices, use brackets instead of parentheses.
Thanks

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回答（2 个）

Stephan
Stephan 2019-7-29
  4 个评论
显示 2更早的评论
azam ghamari
azam ghamari 2019-7-31
Hi, Two days ago I answered you, that I actually read it and I don't know how shall I use the odeXY. please see my answer in below.
and may you please write that code (that I wrote with ode45) with ODEXY?
Thanks and Best Reagards.
Stephan
Stephan 2019-8-1
At the moment im on vacation and have no access to my computer.

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azam ghamari
azam ghamari 2019-7-30
I see it , but I am not sure to undrestand some parts for example:
isterminal(i) = 1 if the integration is to terminate when the ith event occurs. Otherwise, it is 0.
what does it mean exactly?
and I write the code without ode:
clc;
clear all;
close all;
deltat=1;
x1(1)=510;
x11(1)=550;
x1(2)=(0.1*x1(1)-50)*deltat+x1(1);
for i=1:1000
y1(i)=x1(i);
if (x1(i+1)>=550 && x1(i+1)==(0.1*x1(i)-50)*deltat+x1(i))||(x1(i+1)<=550 && x1(i+1)==(0.1*x1(i)-56)*deltat+x1(i))
%return i;
x1(i+2)=(0.1*x1(i+1)-56)*deltat+x1(i+1);
y1(i)=x1(i);
elseif (x1(i+1)<=510 && x1(i+1)==(0.1*x1(i)-56)*deltat+x1(i))||(x1(i+1)>=510 && x1(i+1)==(0.1*x1(i)-50)*deltat+x1(i))
%return i;
x1(i+2)=(0.1*x1(i+1)-50)*deltat+x1(i+1);
y1(i)=x1(i);
end
end
figure(1)
plot(x1)
Iand it gives me the result, and I want to write teh code with ode function , how can I change my before code taht I sent befor (with ode) based on this code in away that I get the result ?(with odeXY that you introduced)
Thanks

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