# Octave Graph Plotting: Axis when x and y = 0

By default, when I plot a graph, the axis seems to be at the lower limit

x=linspace(-10,10,20)
y=4*x+2
plot(x,y)


http://is.gd/f9zOkl

How can I have the axis when x=0 & y=0, for example below

http://www.regentsprep.org/Regents/math/algtrig/ATP8b/inversegraph.gif

UPDATE

If its not possible to use real "axis", I am thinking of plotting the graphs x=0 & y=0 for the y & x axis respectively, how might I do that?

Then isit possble to show where they intersect? like in format like (x, y) eg. (0, 2)

It seems that this is not (easily) possible. For your information: I found the following links:

• Thanks, I am trying to plot graphs of x=0 and y=0 to simulate the y & x axis, how might I do that? See updated post/question – Jiew Meng Aug 28 '11 at 6:16

try this:

set (gca, "xaxislocation", "zero");

set (gca, "yaxislocation", "zero");

It works only for Octave, not Matlab. Would be interesting also to know how do this with matlab.

• I have seen this command in many of the sites but surprisingly it doesn't work in my GNU Octave – Debashish Sep 2 '18 at 18:14

After creating your plot, you could try this which draws lines:

% Keep the current graph
hold;
% Draw X axis
plot([-6 6], [0 0], 'k-'); % Draws a line between x=(-6 to 6) and y=(0 to 0)
% Draw Y axis
plot([0 0], [-5 5], 'k-'); % Draws a line between x=(0 to 0) and y=(-5 to 5)


In plot([-6 6], [0 0], 'k-'); replace -6 with the lower limit for x and 6 with the upper limit.

In plot([0 0], [-5 5], 'k-'); replace -5 with the lower limit for y and 5 with the upper limit.