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matlabplotmatlab-figurehorizontal-line
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Reputation: 4477

How to add a x-axis line to a figure? (matlab)

I want to add a x-axis line at 0 to a Matlab figure so that I can compare my data to see if it is positive or negative when saving the figures to a jpg. What is the best way to do this? I know you can use line() but it just seems cumbersome because you need to specify the x and the y ranges. Is there an easier way?

Upvotes: 16

Views: 59243

Answers (6)

Cris Luengo
Cris Luengo

Reputation: 60645

Since MATLAB R2018b there is yline for this purpose:

 yline(0)

draws a horizontal line at y==0.

Upvotes: 1

Mota Mota
Mota Mota

Reputation: 53

  1. Draw your data by plot() command or stem(). A figure window will open.
  2. Then on the figure window, click on the [insert] command from the
    menu bar, a drop-down menu will appear.
  3. From this menu click on the [line] command, now the shape of the
    cursor will change into a plus sign.
  4. Now you can draw a line anywhere you want, either horizontal or
    vertical or slanted.
  5. You can change the properties of line by right clicking on the
    line, a menu will appear from which you can choose your desires
    properties.
  6. If you want to have some ticks on the line then you can use add text option, and place text where ever you want.
  7. If you would like to have a code for your figure, click on [file] menu and then click on [generatecode] option, a new text editor
    window will open, you can save this code for further use. Good luck.

Upvotes: 1

Jonas Stein
Jonas Stein

Reputation: 7043

A vline and hline command like in GNU R would be great, but I could not find a shorter solution than

plot(1:10,sin(1:10));
line(xlim,[0 0],'Color','r')

Upvotes: 6

Amro
Amro

Reputation: 124563

There exist an undocumented function graph2d.constantline:

plot(-2:5, (-2:5).^2-1)

%# vertical line
hx = graph2d.constantline(0, 'LineStyle',':', 'Color',[.7 .7 .7]);
changedependvar(hx,'x');

%# horizontal line
hy = graph2d.constantline(0, 'Color',[.7 .7 .7]);
changedependvar(hy,'y');

screenshot

The nice thing is that it internally implements a listener for the axes limits (handles change like pan, zoom, etc..). So the lines would appear to extend to infinity.

Upvotes: 32

Vidar
Vidar

Reputation: 4221

You could get this x range directly after the figure has been created. It goes a little something like this:

x=-2:5;
y=x.^2-1;

figure()
plot(x,y);

xlim = get(gca,'xlim');  %Get x range 
hold on
plot([xlim(1) xlim(2)],[0 0],'k')

enter image description here

Note that if you do any manual zooming out in the figure, the line might have to be redrawn to go over the entire new x range.

Upvotes: 7

John Colby
John Colby

Reputation: 22588

I don't believe there is a built-in way that is more convenient. I use hline() and vline() from FileExchange, which work like a charm:

http://www.mathworks.com/matlabcentral/fileexchange/1039

Upvotes: 6

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