How to increase number of contour lines in a plot?

5 views (last 30 days)
Mahmoud Abbas
Mahmoud Abbas on 14 Apr 2022
Commented: Bjorn Gustavsson on 14 Apr 2022
Hello, could you help me make this plot have 20 controur lines and show their respective values on the plot
f = @(x1,x2) (x1-5)^2+(x2-4)^2;
fcontour(f,[0 10 0 10])
colorbar

Answers (2)

Steven Lord
Steven Lord on 14 Apr 2022
f = @(x1,x2) (x1-5).^2+(x2-4).^2; % Vectorized the function
h = fcontour(f,[0 10 0 10]); % Let MATLAB choose the number and height of levels
fprintf("There is a contour at level: %g\n", h.LevelList)
There is a contour at level: 10 There is a contour at level: 20 There is a contour at level: 30 There is a contour at level: 40 There is a contour at level: 50 There is a contour at level: 60
figure
h = fcontour(f,[0 10 0 10], 'LevelList', 0:5:50); % I'll choose the levels
fprintf("There is a contour at level: %g\n", h.LevelList)
There is a contour at level: 0 There is a contour at level: 5 There is a contour at level: 10 There is a contour at level: 15 There is a contour at level: 20 There is a contour at level: 25 There is a contour at level: 30 There is a contour at level: 35 There is a contour at level: 40 There is a contour at level: 45 There is a contour at level: 50
  1 Comment
Mahmoud Abbas
Mahmoud Abbas on 14 Apr 2022
Thank you, this works well however i need the number of contour lines to be exactly 20 and the associated values to be shown in the plot. is this possible?

Sign in to comment.


Bjorn Gustavsson
Bjorn Gustavsson on 14 Apr 2022
If you check the documentation you will find this advice:
fcontour(f,'LevelList',[-1 0 1])
which adapted to your xy-region would be something like:
fcontour(f,[0 10 0 10],'LevelList',[-1 0 1])
HTH
  2 Comments
Bjorn Gustavsson
Bjorn Gustavsson on 14 Apr 2022
That is a simple for you to achieve as modifying the levels in the "LevelList". I couldn't be bothered to figure out where to put them since you might want the somewhere else, but for 20 levels between two values you could do something like:
minVal = 0.5; % Still cannot be bothered to find out, so you have do decide.
maxVal = 13; % same as above.
LevelList = linspace(minVal,maxVal,20);
fcontour(f,[0 10 0 10],'LevelList',LevelList)

Sign in to comment.

Products


Release

R2021b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!