How do errorbars change in logplot?

Question

Wout Laeremans 2023-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/1944014-how-do-errorbars-change-in-logplot

回答： Star Strider 2023-4-9

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Hi all,

I have a collection of data points at every timestep, say at timestep

, I have a collection of points

. For

I have again

and so on. Then I plot the average at every timestep together with the errorbars, giving the 95% confidence interval. My question is now, if I then do:

set(gca, 'YScale', 'log')

What happens to the errorbars? For example, does the average of the errorbar in logspace become the log of the old errorbar or does it become the average of the log of the data points? How exactly thus the rescaling happen?

Thank you in advance for your reply!

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Answer 1

Star Strider 2023-4-9

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1944014-how-do-errorbars-change-in-logplot#answer_1212284

在 MATLAB Online 中打开

The error bars scale with appropriate axis scales, and negative error bars or error bars equal; to zero do not plot at all on a logarithmic axis —

x = 1:10;

y = rand(size(x));

err = randn(size(x))*0.1;

figure

errorbar(x, y, err)

grid

figure

errorbar(x, y, err)

grid

set(gca, 'YScale','log')

Warning: Negative data ignored

(This also neatly illustrates the problem of doing a regression on logarithmically-scaled variables, because the actual errors behave the same way. They are multiplicative, not additive, violating the assumptions of least-squares parameter estimation.)

.