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Pre-determine plot ranges?

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Chris
Chris on 21 Aug 2019
Commented: Chris on 23 Aug 2019
Given two vectors of the same length is there a way to determine the axes ranges that would result if the data were plotted without plotting the data?
I am looking to update xlim and ylim manually after the plotted data is changed* but with out relying on the automatic resizing as there are other things plotted that I dont want to be used in determining the plot ranges. Also I would rather not redraw the entire figure with just the modified data then redraw the larger thing.
(plotted data is changed*: I am manipulating the XData and YData parameter of plotted data directly with a handle.)

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Accepted Answer

Adam Danz
Adam Danz on 21 Aug 2019
Edited: Adam Danz on 21 Aug 2019
If vector1 and vector1 are the x and y values to be plotted, the xlim and ylim for a tight axis would be,
xlim([min(vector1), max(vector1)]);
ylim([min(vector2), max(vector2)]);
If you'd like to access those values from the line object handle 'h',
xlim([min(h.XData), max(h.XData)]);
ylim([min(h.YData), max(h.YData)]);
If you'd like to add 5% of the data range on each side so your max and min data points are not on the axis edges,
xlim([min(x),max(x)] + [-1,1]*.05*range(x))
ylim([min(y),max(y)] + [-1,1]*.05*range(y))

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Adam Danz
Adam Danz on 21 Aug 2019
The 3rd block of code in my answer will add a buffer around your data so the axes are not "tight". If you'd like to take that a step further and make sure the axis limits begin and end at a certain interval (like multiples of 0.5) you easily round those limits.
Here's a demo.
int = 0.5;
xl = [floor(min(x)/int)*int,ceil(max(x)/int)*int];
yl = [floor(min(y)/int)*int,ceil(max(y)/int)*int];
xlim(xl)
ylim(yl)
Adam Danz
Adam Danz on 21 Aug 2019
Your proposal requires that an axis already exists. If you want to base "int" from my solution on the axis tick interval,
int = mean(diff(get(gca,'xtick')));
xl = [floor(min(x)/int)*int,ceil(max(x)/int)*int];
Chris
Chris on 23 Aug 2019
yep good edit. initilization wont be a problem and the changed data points will be of the same magnitude so reusing tick should work.

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