interpolations: Interpolation functions
In McDowellLab/loadflex: Models and Tools for Watershed Flux Estimates

Description Usage Arguments Details Value References See Also

A set of functions that interpolate a y variable over time. See the Interpolation Types section for details specific to each function. These functions are intended for use within loadInterp and loadComp models.

linearInterpolation(dates.in, y.in, dates.out)

triangularInterpolation(dates.in, y.in, dates.out)

rectangularInterpolation(dates.in, y.in, dates.out)

splineInterpolation(dates.in, y.in, dates.out)

smoothSplineInterpolation(dates.in, y.in, dates.out)

distanceWeightedInterpolation(dates.in, y.in, dates.out)

`dates.in`	A numeric vector desribing the dates for each of the values in `y.in`. Dates are represented as the number of seconds since 1970.
`y.in`	A vector of values (typically fluxes or concentrations) to interpolate among.
`dates.out`	A numeric vector of dates for which the corresponding output values are to be produced. Dates are represented as the number of seconds since 1970.

These functions may assume the following without checking:

dates.in is sorted chronologically
y.in is sorted by dates.in
dates.in and dates.out are in the same numeric format

linearInterpolation - straight lines from one point in y.in to the next.

triangularInterpolation - connects each successive pair of points i and j by a straight line from (dates.in[i], y.in[i]) to (mean(dates.in[i], dates.in[j]), 0) to (dates.in[j], y.in[j]). This function was described by Verma et al. 2012 as an option for residuals interpolation with the composite method.

rectangularInterpolation - horizontal lines through each point connected by vertical lines at the midpoint between each pair of dates. This function was described and recommended by Verma et al. 2012 as an option for residuals interpolation with the composite method.

splineInterpolation - a smooth curve that runs through each point in y.in.

smoothSplineInterpolation - a smoothing spline that follows the trends in y.in without passing through each point. This function always uses a fixed set of arguments for smooth.spline (mostly the defaults), while getSmoothSplineInterpolation can produce a smooth spline function with the parameters of your choice.

distanceWeightedInterpolation - An inverse-distance-weighted average of y.in at each dates.out point. This function creates a weight for each y.in based on the distance from dates.in to the values in dates.out. The y.out prediction for each value of dates.out is then the weighted average of the y.in values. This function always uses a fixed inverse-distance function (1/(a-b)^2), while getDistanceWeightedInterpolation can apply the inverse-distance function of your choice.

A vector of values (typically fluxes or concentrations), in the same units and on the same scale as the y.in values, that are the function's predictions for y.out at each of the dates in dates.out.

Verma, S., M. Markus, and R. A. Cooke. 2012. Development of error correction techniques for nitrate-N load estimation methods. Journal of Hydrology 432-433:12-25.

getSmoothSplineInterpolation and getDistanceWeightedInterpolation produce interpolation functions of the form described here, but with flexibility in the values of arguments passed to the internal workhorse functions.

McDowellLab/loadflex documentation built on May 8, 2019, 9:48 a.m.