How can i plot a boundary line in contour plot

Question

mohammad mortezaie 2021-8-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1438419-how-can-i-plot-a-boundary-line-in-contour-plot

评论： Adam Danz 2021-8-23

采纳的回答： Adam Danz

在 MATLAB Online 中打开

Hello,

I have this code for ploting a contour plot.

%bare electron mass (kg)
a=1.855;
eb=-3.276;
ep=-1.979;
t=-1.844;
FS      = 24;	%label fontsize
FSN     = 24;	%number fontsize
LW      = 2;	%linewidth
% Change default axes fonts.
% set(0,'DefaultAxesFontName', 'Times New Roman');
% set(0,'DefaultAxesFontSize', FSN);
% Change default text fonts.
% set(0,'DefaultTextFontname', 'Times New Roman');
% set(0,'DefaultTextFontSize', FSN);
hbarChar=['\fontname{MT Extra}h\fontname{Times New Roman}'];
iform = complex(0.0,1.0);
% Creating necessary k-vectors
kx = linspace(-1.4,1.4,500);
ky = linspace(-2,2,500);
[k_x,k_y] = meshgrid(kx, ky);
phi=exp(-iform.*k_x*a)+2.*exp(iform.*k_x*a/2).*cos(sqrt(3).*k_y.*a/2);
figure (2)
energy_mesh1 = (eb+ep)/2+sqrt(((eb-ep)/2)^2+t^2.*phi.*conj(phi)) ;
energy_mesh2 = (eb+ep)/2-sqrt(((eb-ep)/2)^2+t^2.*phi.*conj(phi));
g=energy_mesh1-energy_mesh2;
contour(k_x,k_y,g,500,'LineWidth',1.5)
colormap('jet');

I want to connect dark points of the contour plot.

What should I do?

5 个评论
显示 3更早的评论隐藏 3更早的评论

Adam Danz 2021-8-23

When I run your code, g contains imaginary numbers which result in an error in contour().

Adam Danz 2021-8-23

I have the same question as @Wan Ji. What are the dark points (your image didn't help) and how do you want to connect them? With lines? Perhaps an illustration would help.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Adam Danz 2021-8-23

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1438419-how-can-i-plot-a-boundary-line-in-contour-plot#answer_772984

编辑：Adam Danz 2021-8-23

在 MATLAB Online 中打开

Copy of original code with the following changes.

contour(k_x,k_y,g,500) chaanged to contour(k_x,k_y,real(g),500)
Commented-out changes to default font properties

%bare electron mass (kg)
a=1.855;
eb=-3.276;
ep=-1.979;
t=-1.844;
FS      = 24;	%label fontsize
FSN     = 24;	%number fontsize
LW      = 2;	%linewidth
% Change default axes fonts.
% set(0,'DefaultAxesFontName', 'Times New Roman');
% set(0,'DefaultAxesFontSize', FSN);
% Change default text fonts.
% set(0,'DefaultTextFontname', 'Times New Roman');
% set(0,'DefaultTextFontSize', FSN);
hbarChar=['\fontname{MT Extra}h\fontname{Times New Roman}'];
iform = complex(0.0,1.0);
% Creating necessary k-vectors
kx = linspace(-1.4,1.4,500);
ky = linspace(-2,2,500);
[k_x,k_y] = meshgrid(kx, ky);
phi=exp(-iform.*k_x*a)+2.*exp(iform.*k_x*a/2).*cos(sqrt(3).*k_y.*a/2);
figure (2)
energy_mesh1 = (eb+ep)/2+sqrt(((eb-ep)/2)^2+t^2.*phi.*conj(phi)) ;
energy_mesh2 = (eb+ep)/2-sqrt(((eb-ep)/2)^2+t^2.*phi.*conj(phi));
g=energy_mesh1-energy_mesh2;
contour(k_x,k_y,real(g),500)
colormap('jet');

Compute the location of lowest values excluding the image edges

% Get lowest points
idx = find(imregionalmax(-real(g)));
% Remove lowest points at edges
[row,col] = ind2sub(size(g),idx);
isEdge = row==1 | row==size(g,1) | col==1 | col==size(g,2);
idx(isEdge) = [];

Compute center and radius of circle

This assumes that the points will lie along the circumference of a circle. If the expected shape is oval, that's an easy change. If the expected shape is unknown, you'll need to sort the points so they are in order and then just plot their connections with a line or compute a polyshape.

% compute circle
xyLoc = [k_x(idx),k_y(idx)];
cnt = mean(xyLoc); 
radius = max(range(xyLoc))/2;
% Plot points and circle
axis equal
hold on
h = plot(k_x(idx),k_y(idx), '*w','MarkerSize', 14);
circ = rectangle('Position',[cnt-radius, [2,2]*radius], ...
    'Curvature',[1,1], 'EdgeColor', 'w');