Fit a periodic smoothing spline to the measurements for each feature as a function of the periodic variable.

## Arguments

- x
Matrix of measurements, with observations in rows and features in columns. Missing values are allowed.

- time
Vector of values of the periodic variable for the observations, where 0 corresponds to the lowest possible value and 1 corresponds to the highest possible value.

- nKnots
Number of internal knots to use for the periodic smoothing spline.

## Value

- xFitMean
Matrix of coefficients, where rows correspond to features and columns correspond to variables in the fit.

- xFitResid
Vector of root mean square of residuals, same length as

`x`

.