How to increase number of contour lines in a plot?

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

Answer 1

[Steven Lord]

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

[Mahmoud Abbas]

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?

Answer 2

[Bjorn Gustavsson]

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

[Mahmoud Abbas]

I tried it but it didn't work and it showed me one contour line. I want the code to plot exactly 20 contours over the specified interval and show their values on the plot

[Bjorn Gustavsson]

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)