Plot curve that is 1 standard deviation away from best fit curve ?
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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
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/159167/image.png)
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.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/159168/image.png)
1 Comment
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.
Answers (1)
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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