How using function Stairs for a market ?

geg

[dpb]

Restore your original posting for context, Julien...

Answer 1

[dpb]

S = [400 500 200];       % supply
PS = [15 25 55];         % Price supply
[PS,iPS]=sort(PS);       % sort price ascending; keep in order with supply
S=S(iPS);                % rearrange supply with sorted price
[PD,iPD]=sort(PD,'descend');
D=D(iPD);
figure
stairs([0 cumsum(S)],[PS PS(end)])
ylim([0 70])
hold on
stairs([0 cumsum(D)],[PD PD(end)],'r-')

yields: