# How to plot several confidence intervals together?

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Commented: John D'Errico on 16 Feb 2018
Hi, I need to plot three regression lines and their confidence interval, all in one plot. It would be something like the attached plot that is created by SAS.
Any idea how to do this in MATLAB?
Thanks!

John D'Errico on 13 Feb 2018
Can you plot ONE regression line with a confidence band around it? Of course. The CI is trivial - basic stats.
You can plot the CI band as a patch. So plot it as a polygon, filled with your choice of color. Patch or fill will work here. Make it semi-transparent, so alpha around 0.2 or so.
Then learn how to plot additional curves on one figure, one set of axes. Thus learn how to use the hold command, to cause MATLAB to plot a second curve (and associated confidence band) onto an existing figure.
All easy. Just read the help and examples for a few functions. Spend some time learning the basic stats if you need that to learn how to compute the CI band.
Hi John, I faced a problem here. The CI band is usually expanding at the ends and narrows in the middle but when I use 'patch' or 'fill' it doesn't do that. Please let me know what you think. I attached two figs to show you what I mean.
Thanks,
John D'Errico on 16 Feb 2018
Of course it does not fill it. You need to create the CI bands as ONE curve, NOT as two curves. Go up along one bound, then down to the second, and back along the second curve, with the second curve flipped in sequence so you traverse it backwards. The result will be a closed polygonal region. Then tools can be used to fill that region with your desired color.