tempeffformula to specify the variable with a smooth effect. The function does not fit the model, it simply returns information exploited by
seas(x, ndx = stop("please, provide `ndx' in seas()"))
nis the time series length.
tempeff()when the long term trend of the daily time series is fitted via a smooth term. A standard P-spline with a cubic B-spline basis and a second-order difference penalty is employed.
Wood, S.N. (2006) Generalized Additive Models: An Introduction with R. Chapman and Hall/CRC Press.