Is this a bug?

Is this a bug?

clear all;

figure(1);

stem([1 2],[pi 2]);

(the pi entry does not appear in the plot) Thanks

[sa]

Is it just me who gets this result?

figure;

stem([1 2],[pi 2], 'LineWidth', 3);

grid on;

%xlim([0 4]); %<-commenting this makes the pi disappear. replacing pi with anything else also fixes the problem!

[sa]

I am using 2011b on 64 bit computer (though this is probably irrelevant)

[sa]

If you see the pi entry at x=1 try rescaling the stem window, the pi seems to disappear randomly

Answer 1

[Image Analyst]

No, it's doing what it should. They both appear, maybe you just don't see it. Try this code:

figure;
stem([1 2],[pi 2], 'LineWidth', 3);
grid on;
xlim([0 4]);

You'll see that there is a stem at both x=1 with height 3.141 and at x=2 with height 2. Of course there is no stem at x=pi since pi was the y value not the x value - was that what you were expecting? The x values are the first array and the y are the second, like [x1 x2 x3], [y1, y2, y3]. It is not [x1, y1], [x2, y2], [x3, y3].

[sa]

:) I was expecting pi at x=1

[sa]

Thanks I didn't realize that until just now!

Yes it seems to come and go reandomly.

Its actually somewhat important cause I spent an hour trying to debug my code before realising it was stem that was doing it.

[Image Analyst]

Perhaps it is a bug. The stem at x=1, y=pi seems to come and go depending on the size of the figure. As I drag the figure wider it will randomly appear and disappear depending on what size I set the figure to. Maybe it's a subsampling/aliasing issue with the display resolution. I can't get the behavior when the left stem is not lying on the Y axis (like you get when you widen the x axis with xlim so that the left edge is at x=0 and not x=1).

[sa]

When I replace Pi with integers the scaling does nothing.