# The plot of this discontinous values does not work.

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Stefan Henning on 18 Feb 2015
Commented: Stefan Henning on 18 Feb 2015
Dear Matlab Community,
I got a problem plotting this discontinous geometry. There are no erros, but The plot is empty, just filled with some dots, that are even hard to realize :-( I really need to plot with x defined as a vector using linspace, like I did. I have no clue how to solve this problem. I would be very thankful if someone could help me out.
Thank you! Stefan
Here is the code I try to plot:
clc
clear all
close all
%Parameter:
R=2;
h=1;
L=10;
B = 5;
x=linspace(0.0,(2*R+L),100);
hmin = h/2;
if (x < R)
y2 = (R+hmin)-sqrt((R+hmin)^2-((R+hmin)^2-R^2+(x-R).^2));
y2_neg = -y2;
elseif (x > (L+R))
y2 = (R+hmin)-sqrt((R+hmin)^2-((R+hmin)^2-R^2+(x-R).^2));
y2_neg = -y2;
else
y2 = hmin;
y2_neg = -y2;
end
plot(x,y2,x,y2_neg);
grid on
title('Geometrie der Gelenkkontur')
xlabel('s = [0:L]')
ylabel('H(x)')
axis equal

Erik S. on 18 Feb 2015
I send you a file, is it the result you need?
Stefan Henning on 18 Feb 2015
Sure :) Again, thanks a lot!

Erik S. on 18 Feb 2015
Your y2 and y2_neg variables are not vectors, only scalars You can make a loop and compute the y2 and y2_neg for each value of x instead
Stefan Henning on 18 Feb 2015
Thanks for the quick answer! I changed it to:
for x=0:0.1:(L+2*R)
if (x < R)
y2 = (R+hmin)-sqrt((R+hmin)^2-((R+hmin)^2-R^2+(x-R).^2));
y2_neg = -y2;
elseif (x > (L+R))
y2 = (R+hmin)-sqrt((R+hmin)^2-((R+hmin)^2-R^2+(x-R).^2));
y2_neg = -y2;
else
y2 = hmin;
y2_neg = -y2;
end
plot(x,y2,x,y2_neg);
grid on
title('Geometrie der Gelenkkontur')
xlabel('s = [0:L]')
ylabel('H(x)')
axis equal
end
But now I get Errors and an empty plot. I have to say I am new to matlab and do not find the problem here.. Thanks!

Erik S. on 18 Feb 2015
There are a couple of issues. First you get complex numbers ( at least I get it when I run your code) so somehow you take the sqrt of a negative value. Secondly you overwrite your plot in every iteration. I would recommend to create vectors inside the loop (i.e. make y2 and y2_neg vectors) and run the plotting command outside the loop