MATLAB: How to draw a line on top of an imagesc

imagsclineMATLABplot

When I issue a plot command, the previously drawn image disappears and is replaced by the line.

Best Answer

Use hold on

imagesc(yourImage);
hold on;
line([x1,x2], [y1,y2], 'Color', 'r');

Related Solutions

MATLAB: How to join two set of points using scatter command

x1=1:10; y1=1:10;
new_x1 = x1;
new_y1 = y1*2;
cmap = colormap(jet(length(x1)));
figure(1);
scatter(x1,y1,[],cmap,'Marker','d');
hold on;
scatter(new_x1,new_y1,[],cmap,'Marker','*');
hold off;
for i = 1:length(x1)
line([x1(i),y1(i)],[new_x1(i),new_y1(i)],'Color',cmap(i,:));
end

MATLAB: Plot contour lines on top of imagesc

You can specify x/y for imagesc so that the image is not shown against its index. From there you can simply use hold on and contour:

y = [1:10]';
x = 1:0.01:10;
z = repmat(y, [1,901]) - repmat(x, [10,1]);
figure
subplot(2,1,1)
contourf(x,y,z)
xlabel('x (continuous)');
ylabel('y (discrete)')
subplot(2,1,2)
imagesc(x,y,flipud(z))   %specify x/y
xlabel('x (continuous)');
ylabel('y (discrete)')
colormap(jet(256))
hold on  %hold it on
contour(x,y,flipud(z),'color','k') %contour over it

More per Comments

In that case I would grab the 'CData' from the image and bin it using histc (essentially replacing image values with indexes into contour levels). Then draw a contour plot of this.

y = [1:10]';
x = 1:0.01:10;
z = repmat(y, [1,901]) - repmat(x, [10,1]);
figure
subplot(2,1,1)
contourf(x,y,z)
xlabel('x (continuous)');
ylabel('y (discrete)')
subplot(2,1,2)
h = imagesc(x,y,flipud(z));
xlabel('x (continuous)');
ylabel('y (discrete)')
colormap(jet(256))
hold on
D = get(h,'CData'); %image data
[~,idx] = histc(D,linspace(m(min(D)),max(max(D)),10)); %bin it
contour(x,y,idx,'color','k') %contour of the bins

Best Answer

Related Solutions

MATLAB: How to join two set of points using scatter command

MATLAB: Plot contour lines on top of imagesc

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