upper and lower curves

I uesed the basic fitting to get the 5th polynominal curve (median) .

I want to add the upper with 25% from the median and lower with 25% from median curves.

Answer 1

[Matt J]

You can use the quantile command

https://www.mathworks.com/help/stats/quantile.html

to determine the upper and lower quartiles at each time points and then use those points to plot the upper and lower curves.