# Drawing a line through the peak of the plot

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Mst Ismita Tasnim on 21 Jan 2023
Commented: Paul on 21 Jan 2023
I have a plot as follows. How can I add vertical lines through the peak points (total 3 lines here) in the plot ?
Code:
I have written the code as:
"clear all;
m = 4.48e-26; % mass of Nitrogen molecule
k = 1.38e-23; % Boltzmann Constant
p = 0:2800;
ind = 1;
for T = 300:500:1500;
% constant computation
c1 = 4*pi*(m/(2*pi*k*T))^(3/2);
c2 = m/(2*k*T);
c3 = 3*m*k*T;
u(ind,:) = c1*(p.^2.*exp(-(c2*p.^2)));
%u2(ind,:) = c1*c3*exp(-(3/2))
ind = ind+1;
end
figure(1)
plot(p,u)
xlabel('P')
ylabel('probability')
" Walter Roberson on 21 Jan 2023
xline()

Paul on 21 Jan 2023
m = 4.48e-26; % mass of Nitrogen molecule
k = 1.38e-23; % Boltzmann Constant
p = 0:2800;
ind = 1;
for T = 300:500:1500;
% constant computation
c1 = 4*pi*(m/(2*pi*k*T))^(3/2);
c2 = m/(2*k*T);
c3 = 3*m*k*T;
u(ind,:) = c1*(p.^2.*exp(-(c2*p.^2)));
%u2(ind,:) = c1*c3*exp(-(3/2))
ind = ind+1;
end
figure(1)
plot(p,u)
xlabel('P')
ylabel('probability')
Find the maximum points and their corresponding indices
[maxu,index] = max(u,[],2);
Plot vertical lines at p for each index. Use the options for xline to customize color, etc.
xline(p(index(1)));
xline(p(index(2)));
xline(p(index(3))); ##### 2 CommentsShowHide 1 older comment
Paul on 21 Jan 2023
Check out the doc page for max. Freel free to come back if you still have questions.