Only plot outline of graph

this is my code:

% Plot the conductivity levels along the line (as an outline)
figure;
plot(lineX, conductivityValues, 'k-', 'LineWidth', 1.5, 'Marker', 'none');
xlabel('X [m]');
ylabel('Conductivity');
title(['Conductivity along Y = ', num2str(targetY)]);
box on

and now i get this plot:

I only wantt to plot the outline of this plot how do I do this?

[Dyuman Joshi]

Sort the x values and get the corresponding indices.

Then plot the x values vs y values sorted according to the indices.

[Lara]

Thank you. I get this graph:

Is there a way to only plot the outline of this plot without using the scatter function?

[Star Strider]

Perhaps taking the maximum of the ‘conductivityValues’ will give you that.

[Matt J]

It is always advisable to attach a .mat file of sample input data to accompany your code, so that the forum can more easily develop and demonstrate solutions.

[Dyuman Joshi]

You can plot the local maximas -

% Numerical data (generated as an example)
% Taken from Matt J's answer
N = 1e3;
t = linspace(-4, 2, N);
R = randn(1,N);
y = sin(t) + 0.5*sin(2*t) + 0.2*sin(3*t)+cos(t) + 0.5*cos(2*t) + 0.2*cos(3*t)+.2*R;
IND = (y<0);
y(IND)=abs(y(IND));

idx = islocalmax(y);

plot(t, y, t(idx), y(idx), 'k--')

Answer 1

[Matt J]

Use movmax to get the upper envelope of a sequence of data points, and possibly smooth it with sgolayfilt, e.g.,

% Numerical data (generated as an example)
N = 1e3;
t = linspace(-4, 2, N);
R = randn(1,N);
y = sin(t) + 0.5*sin(2*t) + 0.2*sin(3*t)+cos(t) + 0.5*cos(2*t) + 0.2*cos(3*t)+.2*R;
IND = find(y<0);
y(IND)=abs(y(IND));

yupper=sgolayfilt( movmax(y,25), 4,41);

% Data is Plotted 
plot(t, y, t,yupper,'LineWidth', 1.5);
legend('Data','Outline',Location='northwest')

Answer 2

[Sulaymon Eshkabilov]

In this exercise, envelope() with 'peaks' options does a good job, e.g.:

% Numerical data (generated as an example)
N = 1e3;
t = linspace(-4, 2, N);
R = randn(1,N);
y = sin(t) + 0.5*sin(2*t) + 0.2*sin(3*t)+cos(t) + 0.5*cos(2*t) + 0.2*cos(3*t)+.2*R;
IND = find(y<0);
y(IND)=abs(y(IND));

% Data is Plotted 
plot(t, y, 'LineWidth', 1.5, 'DisplayName','Data');
hold on;
% Envelope function is applied
[UP, ~] = envelope(y,15, 'peaks');
% UPPER Envelope is plotted  
plot(t, UP, 'k-', 'linewidth', 2.5, 'DisplayName','Outer Profile Shape')
legend('Location', 'Best')
hold off;