plotting functions with different sizes

s=1; xs=1.5836; vp=1; k=0.63; em=2.5; ppu=0.8; ps=0.95; sm=10;
q=-s:0.001:s;
stepE=vp:0.001:0.9*em;
radRNG=(stepE*vp)/xs;
r=radRNG-k;
y=(r-ppu*(sm/100));
if y<0
    y=-y;
end
x=-(sqrt((r).^2-((y).^2)));
n=length(q);
for i=1:n
    if q(i)>=-k & q(i)<=(0.9*em*vp)./xs
        p(i)=sqrt(r.^2-x.^2);
    elseif q(i)>=(0.9*em*vp)./xs & q(i)<=ps
        p(i)=sqrt(s.^2-q(i).^2);
    elseif q(i)>ps & q(i)<=s
            p(i)=0;
   
    end
end
p(p>ppu)=ppu;
figure(1)
plot(q,p)
ylim([0 s])
xlim([-s s])
xlabel('Q in p.u'); ylabel('P in p.u')

How can I plot these functions assuming i have different sizes ? I have x and y as points in first if statement with different size than q and i want to plot

[Cris LaPierre]

Your code has an error preventing it from running.

Line 6 has this error:

Unrecognized function or variable 'ppu'.

[Osama Aliwat]

Oh im sorry , i forgot to put in the value of ps , which is 0.95

[Osama Aliwat]

Also i forgot the value of ppu , i edited it again.

[DGM]

1: sm is undefined

2: This is assigning a vector to a single element of another vector

p(i)=sqrt(r.^2-x.^2);

3: You say "how can i plot these functions" -- Other than p, which functions?

[Osama Aliwat]

Thank you for your reply , sm=10 , by functions i mean the equations in if statement , the second and third i can plot them if i remove the first if statement , but the when i add the first if statement that in the equation has x and y , they have different lengths so its not possible to plot them togther , so i wanted to know if there is a way that i can do so

[Osama Aliwat]

clc
clear
s=1; xs=1.5836; vp=1; k=0.63; em=2.5; ppu=0.8; ps=0.95; sm=10;
stepE=(vp):0.01:em*0.9;
radRNG=(stepE*vp)/xs;
r=radRNG-k;
y=(r-ppu*(sm/100));
x=(sqrt((r).^2-((y).^2)));
radRNG2=(0.9*em*vp)/xs;
r2=radRNG2-k;
y2=(r2-ppu*(sm/100));
x2=-(sqrt((r2).^2-((y2).^2)));
q=-s:0.001:s;
n=length(q);
for i=1:n
    if q(i)>=x2 & q(i)<=ps
        p(i)=sqrt(s.^2-q(i).^2);
    elseif q(i)>ps & q(i)<=s
            p(i)=0;
   
    end
end
p(p>ppu)=ppu;
figure(1)
plot(x-k,y+ppu*(sm/100),q,p)
ylim([0 s])
xlim([-s s])
xlabel('Q in p.u'); ylabel('P in p.u')
grid

After adjusting the code , this is the best i could get to where the could run , but as seen from the graph , im getting two different lines and couldnt manage to put it into single line.

[KSSV]

You need to rethink on your code. What exactly you are trying to achieve?

[Osama Aliwat]

I am trying to plot capability curve for a generator.

the curve should look like this

[DGM]

It almost looks like you're trying to plot a piecewise 1D function of q, but your intervals all overlap, so I have no idea what you're actually trying to plot.

% your plotting intervals in terms of q:
% interval 1 is [-k (0.9*em*vp)/xs]
% interval 2 is (-inf ps] & [(0.9*em*vp)/xs inf)
% interval 3 is (ps s]

% so the intervals stack up like 
%           [-0.63 -------------- 1.42]
% (-inf --------- 0.95]           [1.42 -------------- inf)
%                  [0.95 -- 1.00]

% but q is only defined over [-1 1]

Furthermore, the function that would be plotted in interval 1 isn't even a function of q, so the idea that this is a piecewise function of q doesn't make much sense to me. In fact, this whole thing:

if y<0
    y=-y;
end
x=-(sqrt((r).^2-((y).^2)));
% ...
p=sqrt(r.^2-x.^2);

Is a convoluted way of saying:

p = abs(y);

I don't even see that x or y are used for anything else.

You're going to have to figure out what you're trying to plot and how you want it plotted. I can't tell.