Warning: Negative data ignored

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Bharat
Bharat 2013-4-5
I want to know how to plot negative value. I have imported data from excel file to plot in matlab. In data i have negative value but i can't able to see graph at negative value.
Plz help to find solution. And how to do to see negative curve.
plot(freq,x);hold all;plot(freq,y);hold off;figure(gcf);
Warning: Negative data ignored
Warning: Negative data ignored

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回答（3 个）

Tom Lane
Tom Lane 2013-4-6
Could you have already had "hold on" in effect for a plot with log axes? The following commands illustrate what I mean:
semilogy(rand(10,1),rand(10,1),'bo') % you could get the error by doing this,
hold on % then turning hold on,
plot(rand(10,1),randn(10,1),'rx') % <- if your code fragment started here
Image Analyst
Image Analyst 2013-4-5
Try using "hold on" instead of "hold all".
  2 个评论
Jan
Jan 2013-4-5
Why? "hold all" cares about the color order also, as far as I remember.
Image Analyst
Image Analyst 2013-4-5
I thought that maybe hold all would lock down the Y axis limits and then if you tried to plot y outside of those limits, then it might not be able to plot some. It was just a guess.

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Jan
Jan 2013-4-5
编辑：Jan 2013-4-5
The shown code works with negative values also:
freq = 1:10;
x = linspace(-5, 5, 10);
y = linspace(5, -5, 10);
plot(freq,x);
hold('all');
plot(freq,y);
hold('off');
figure(gcf);
Therefore something else must be going wrong. Perhaps you have set any properties or other GUI obejcts to invalid values before, e.g. the 'Value' of an uicontrol to -1. Please post the relevant part of the code then.

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