创建具有变化的轴值的水平线和垂直线？ （MatLab）

Question

I am trying to plot both horizontal and vertical lines on a histogram that will be accurate to changing limits on both the x and y axes. I was using the line(X,Y) function, but cannot find a useful way to get the lines to be set depending on the parameters of the graph window.

Answer 1

I'm not entirely clear on what you want but here's the simplest answer to what I think you want:

Makes a sample histogram

y = randn(100,1);
hist(y,10)

Get the current limits of the x and y axes

xlimits = get(gca, 'XLim');
ylimits = get(gca, 'YLim');

Computes a single numeric value to plot a horizontal line.You'll want to replace this with your specific function of the axes limits

halfpt = ((ylimits(2)-ylimits(1))/2) + ylimits(1);
line(xlimits, [halfpt halfpt])

I'm not sure, but from your comment I'm suspecting that you aren't changing your axes programmatically, with say set(gca,'Xlim', [0 10]) but that you want to be able to drag the axes of your your figure with the mouse, say by using that hand/pointer button in the figure editor. In which case, one solution is to make your figure a GUI and write a callback function that handles line plotting that is a function of the xlim and ylim . Here's an example that always keeps the line in the middle of the axes regardless of how they are dragged:

function myGUI
figure('WindowButtonMotionFcn',@myCallback)
y = randn(100,1);
hist(y,10)

function myCallback(src,eventdata)
xlimits = get(gca, 'XLim');
ylimits = get(gca, 'YLim');
halfpt = ((ylimits(2)-ylimits(1))/2) + ylimits(1);

lh = findall(gcf,'Type','Line');
delete(lh);
myline = line(xlimits, [halfpt halfpt])

end

end