How to add a 1:1 reference line

Hi, I am trying to add a dashed 1:1 reference line to subplots of data correlations. The range of values is the same for both x and y.

I have tried refline, but it appears to be tied to the range of the data, such that it only extends across the plot where there are data points.

For example:

In the plot above, the 1:1 line stops short of the lower-left and upper-right corners. I want a line that goes all the way from the point of origin to the upper right-hand corner of the plot, such as in this plot:

It only works in this graph because there are data points closer to the corners. I want a line that is not dependent on the data, like xline or yline, but has a slope of 1.

Any help is greatly appreciated!

Answer 1

[Star Strider]

I am not certain what you want.

Try this:

x = rand(1,10);                                 % Create Data
y = rand(1,10);                                 % Create Data

figure
plot(x, y, '.')
hold on
plot(xlim, ylim, '--r')
hold off
legend('Data', 'Reference Line', 'Location','SE')

.

[Ellen Maas]

Thank you for the response. I've edited my post to show an example of what I want. The code you suggested results in the original graph looking like this:

[Star Strider]

My pleasure!

Try this (with your values for ‘x’ and ‘y’):

figure
plot(x, y, '.')
hold on
plot([0 max([xlim ylim])], [0 max([xlim ylim])], '--r')
hold off
legend('Data', 'Reference Line', 'Location','SE')

I’m still not certain what you want, however this may get closer.

[Ellen Maas]

Closer, but still limited by the data at the max end and therefore not extending all the way to the upper right-hand corner of the graph. I need the line all the way to the corner.

I'll also add that this code is generating several graphs with different ranges of data, including different scales (0.9 to 1.5 in this case, 2000 to 5000 in another graph, and others in-between).

[Ellen Maas]

So I just tried this, and it works for all the graphs and axis ranges:

plot([0 ylim*2], [0 ylim*2], '--r')

Now the line extends all the way across. None of my axes are less than 0, so having 0 as the minimum value will not cause any problems.

Thank you for your help in thinking this through!

[Star Strider]

As always, my pleasure!

If any are less than 0, an extension of this idea will work similarly:

plot([min([xlim ylim]) max([xlim ylim])], [min([xlim ylim]) max([xlim ylim])], '--r')

That generalises it to any range.