Multiply constraint set by matrix (K*X)

[Marc Wijnand]

I have a constraint set X. Now I want to determine the set Z of elements that is defined as {Z=K*x l x element of X} with K a given matrix [LQR].

I don't understand why the command

plot(Z,z)

gives no result - this should be a line in 1D - while you can verify that Z is not empty by plotting

plot(Z)

.

Minimal working example:

%% K*X in Yalmip

x = sdpvar(2,1);

X = [-1<=x<=1];

K=[1 1];

z = sdpvar;

Z = [z==K*x, ismember(x,X)];

plot(X,[],'g')

plot(Z,z) %no result

plot(Z)

[Johan Löfberg]

No, the plotting functionality does not plot simple lines with no interior

[Johan Löfberg]

You can edit lmi/plot though. Change the plotSet function to 

if size(x_opt,1)==1

    p = line(x_opt,[0 0],'color',color);

    set(p,'LineStyle',options.plot.wirestyle);   

    set(p,'LineStyle',options.plot.wirestyle);   

    set(p,'LineWidth',options.plot.linewidth);

    set(p,'EdgeColor',options.plot.edgecolor);

    set(p,'Facealpha',options.plot.shade);    

elseif size(x_opt,1)==2

and in the same file in generateBoundary, you change the creation of c to

 if length(x)==2

        c = [cos(angles);sin(angles)];

    elseif length(x) == 1

        c = [-1 1];n = 2;

    else

        c = randn(3,n);

    end

[Marc Wijnand]

Thank you!