piecewise function

[wnn666666]

Hello teacher, how to define the segmentation function in yalmip?
The use implies that the following problem occurs.
F=[F,implies(u1(1),[f1<=f1min,uf1==1])
implies(u1(2),[f1min<=f1<=f1min1.5,uf1==(1.5f1min-f1)/(0.5f1min)])
implies(u1(3),[f1>=f1min1.5,uf1==0])
sum(u1(n,:))==1];
Here u1 is the 0-1binvar variable,f1 is the sdpvar variable,f1min Is a number. uf1 is part of the objective function. When I run, it's not possible to report an error.
But when I set one of the conditions u1(2)==1, it works, why is that?
Why not choose one of the three？

[johanlofberg]

I have no idea what you mean with "When I run, it's not possible to report an error"

And please put the code in a code block

[johanlofberg]

and you are using u1(1) when you appear to mean u1(n,1) etc

[wnn666666]

I'm sorry I didn't make myself clear.Here u1 is the 0-1binvar variable,f1 is the sdpvar variable,f1min Is a number.
The specific code is as follows:

u1=binvar(1,3);
uf1=sdpvar(1,1);
F=[F,sum(u1) == 1];
F=[F,implies(u1(1),[f1<=f1min,uf1==1])];
F=[F,implies(u1(2),[f1min<=f1<=f1min1.5,uf1==(1.5f1min-f1)/(0.5f1min)])];
F=[F,implies(u1(3),[f1>=f1min1.5,uf1==0])];

uf1 is part of the objective function，However, the running result is not feasible.I just want to express that different f1 ranges cause different uf1 values.

However,When I set one of the conditions to be met

F=[F,u1(2)==1];
F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])];

The problem is solvable. What is the reason for this?

[johanlofberg]

You would have to supply a reproducible example, because there is no way in a sensible model that the first would be infeasible and the second feasible

...and again, use code blocks (<> in the menu) to make code readable. I've edited you second block to illustrate

[wnn666666]

Sorry about the block I'm not really sure how to output the block. &nbsp; This is a screenshot of the code&nbsp; &nbsp;.As I said before, uf1 is part of the objective function and f1min is a number.What exactly is wrong with this piecewise function?

…

------------------&nbsp;原始邮件&nbsp;------------------ 发件人: "yalmip/YALMIP" ***@***.***&gt;; 发送时间:&nbsp;2024年4月1日(星期一) 晚上7:49 ***@***.***&gt;; ***@***.******@***.***&gt;; 主题:&nbsp;Re: [yalmip/YALMIP] piecewise function (Discussion #1393) You would have to supply a reproducible example, because there is no way in a sensible model that the first would be infeasible and the second feasible ...and again, use code blocks (<&gt; in the menu) to make code readable. I've edited you second block to illustrate — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.Message ID: ***@***.***&gt;

[johanlofberg]

I cannot run a screenshot...

To put code in a code block, just mark it and press <> in the editor (or look at the code I edited and see what the mark-up is)

[wnn666666]

u1=binvar(1,3); uf1=sdpvar(1,1); F=[F,sum(u1) == 1]; F=[F,implies(u1(1),[f1<=f1min,uf1==1])]; F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])]; F=[F,implies(u1(3),[f1>=f1min*1.5,uf1==0])]; Is that right？Sorry I didn't see an example of the format.

[johanlofberg]

well, you put it in a code block, but you messed up spaces and line-breaks

and that code is not reproducible as I cannot run it

[wnn666666]

u1=binvar(1,3);
uf1=sdpvar(1,1); 
F=[F,sum(u1) == 1]; 
F=[F,implies(u1(1),[f1<=f1min,uf1==1])]; 
F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])];
F=[F,implies(u1(3),[f1>=f1min*1.5,uf1==0])];

[wnn666666]

How about this time

[johanlofberg]

as I said, you have to supply reproducible code

[wnn666666]

But I've shown here that it's replicable.

[johanlofberg]

https://en.wikipedia.org/wiki/Minimal_reproducible_example

[wnn666666]

u1=binvar(1,3);
uf1=sdpvar(1,1); 
F=[F,sum(u1) == 1]; 
F=[F,implies(u1(1),[f1<=f1min,uf1==1])]; 
F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])];
F=[F,implies(u1(3),[f1>=f1min*1.5,uf1==0])];

That doesn't work either? I'm sorry I can't get this website open

[johanlofberg]

>> u1=binvar(1,3);
uf1=sdpvar(1,1); 
F=[F,sum(u1) == 1]; 
F=[F,implies(u1(1),[f1<=f1min,uf1==1])]; 
F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])];
F=[F,implies(u1(3),[f1>=f1min*1.5,uf1==0])];

Unrecognized function or variable 'F'.
 
>> 

[wnn666666]

F is the constraint that was defined before. uf1 here is related to the value range of f1, and uf1 is a part of the objective function, the specific code is as follows.f1 and f2 have expressions, f1min and f2min are just numerical values.

F=[];
u1=binvar(1,3);
u2=binvar(1,3);
uf1=sdpvar(1,1); 
uf2=sdpvar(1,1); 
F=[F,sum(u1) == 1]; 
F=[F,implies(u1(1),[f1<=f1min,uf1==1])]; 
F=[F,implies(u1(2),[f1min<=f1<=f1min*1.5,uf1==(1.5*f1min-f1)/(0.5*f1min)])];
F=[F,implies(u1(3),[f1>=f1min*1.5,uf1==0])];
F=[F,sum(u2) == 1]; 
F=[F,implies(u2(1),[f2<=f2min,uf2==1])];      
F=[F,implies(u2(2),[f2min<=f2<=f2min*1.5,uf2==(1.5*f2min-f2)/(0.5*f2min)])];
F=[F,implies(u2(3),[f2>=f2min*1.5,uf2==0])];
 f4=-(0.5*uf1+0.5*uf2);
options=sdpsettings('debug',1,'verbose',2,'solver','gurobi');
result1=optimize(F,f4,options);

[johanlofberg]

Unrecognized function or variable 'f1'.