Creating a polynomial data set

Hi all,

im currently trying to create a polynomial output of my data, basically i have a data set containing time (in seconds ( X axis)) and a tide height in meters ( Y axis) when plotted the tide data over the time series is very noisy due to wave / wind action on the vessel changing the elevation of the recording device.

so to account for this i wish to create a fitted polynomial data set under a new variable name which i can output independently of the original tide variable. this will also account for times where my measuring devise failed and im interpolating data

so far to evaluate which degree of polynomial best fits the data set i have been using the code'

poly3=(fit(time,tide,'poly3','Normalize', 'on'); % clearly i change the 'poly3' value depending upon the degree i need

this works fine for estimating a best fit from a plot of the above variable, but how do i get from this point to creating an adjusted tide height using the polynomial curve i have created.

Regards Gavin

Answer 1

[Amit]

you can do

tide_new = feval(poly3,time); % adjusted tide height

[Gavin]

Thanks Amit this works perfectly. :)

Answer 2

[Jos (10584)]

Take a look at POLYFIT and POLYVAL as well:

PFpar = polyfit(time, tide, 3)
AdjustedTide = polyval(PFpar,time)