About Ylim

Hello everyone ! I want to plot a curve with positive and negative values on the Y-axis. I want to limit the figure to positive values so Ylim starts from 0, but I also want the high limit to be in mode auto. Is there a way to do so ? Thanks for your replies

Answer 1

[Jan]

set(gca, 'YLim', [0, inf]);

Then Matlab uses the hard coded lower limit 0 and the upper limit from the drawn data.

[Daniel Shub]

This is a little bit different then how I interpreted the question. If you use ylim([-inf, inf]), the y limits are tight to the data in the plot. When you use a YLimMode of auto, the y limits are "rounded" to nice values. I thought that Lara wanted the nice rounding.

[Jan]

@Daniel: Correct. Using Grzegorz' method considers the autoscaling. But the auto-scaling is affected by setting the lower limit recursively, see:

x = rand(1, 100) - 0.9; subplot(1,2,1); plot(x); subplot(1,2,2); plot(max(0, x));

Is there a public description of the auto-limit algorithm?

[Marcel]

is there any new knowledge about the question, how the auto-limit algorithm looks like?

for performance reasons I try to avoid the "auto" mode, I believe a self coded function can be way faster... THANKS

Answer 2

[Daniel Shub]

I set the YLimMode to auto in case you have already specified a ylim value. If the max of ylim is less than 0, you need to set the ylim to something else (in this case [0, 1]).

set(gca, 'YLimMode', 'Auto');
set(gca, 'YLim', [0, max([1, max(ylim)])]);

Answer 3

[Grzegorz Knor]

Get ylim value from current axis, and then set limit from zero to maximum (second) value:

plot(randn(1000,1))
yl = get(gca,'ylim');
ylim([0 yl(2)])