Plot curve that is 1 standard deviation away from best fit curve ?

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RuiQi
RuiQi on 22 Dec 2016
Answered: Star Strider on 22 Dec 2016
I have a plot that is quite noisy. I am able to fit it with a straight line using the poly fit line method with bisquare weights. https://www.mathworks.com/matlabcentral/answers/317817-how-to-use-least-squares-fit-with-bisquare-weights
I am now wondering if someone knows how I can fit a curve and maybe even plot the line that is roughly 1 standard deviation from the plotted curve. I am basically trying to get 2 lines that will encompass a large amount of the points. Maybe it could look something like that.. where the red represents the best fit curve and the green the plot that is 1 standard deviation away? The lines below are drawn in paint btw.
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David Barry
David Barry on 22 Dec 2016
That's an interesting fit you have come up with. Not sure I would agree with it but it's difficult to tell with the Y axis scale you have plotted on.

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Answers (1)

Star Strider
Star Strider on 22 Dec 2016
Since you’re using polyfit, you can use the File Exchange polypredci (link) function. It defaults to 95% confidence intervals, so if you want one standard deviation, use 67% confidence intervals.

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