interpolate: Interpolation
In phonTools: Tools for Phonetic and Acoustic Analyses

Description Usage Arguments Details Value Author(s) References Examples

Piece-wise cubic or linear spline interpolation.

1 2	interpolate (y, x = 1:length(y), steps = 20, increment = -1, show = FALSE, type = 'cubic', ...)

`y`	A vector of 'knots', between which the function will interpolate points.
`x`	The 'x' coordinates corresponding to each knot. If not specified, the knots are assumed to be equally spaced.
`steps`	The number of interpolating steps between each knot. Increasing this number will result in a smoother interpolation. If the knots are not equally spaced along the x-axis, the interpolated points will not be equally spaced across the entire curve.
`increment`	If this is greater than 0, interpolated points are separated along the x-axis by this value. Note that if the knot locations are not multiples of this increment, there will be irregularities in the spacing of the interpolated points.
`show`	If TRUE, the result of the interpolation is shown in a plot.
`type`	If 'cubic', a natural cubic spline interpolation is performed. If 'linear', a linear interpolation is performed.
`...`	Additional arguments are passed to the internal call of plot() if show = TRUE.

By default, this function performs a 'natural' cubic spline interpolation between the points provided by the user. Optionally, a linear interpolation between the points may be carried out.

A dataframe with columns corresponding to the x and y dimensions of the interpolated points is returned.

`x`	The x-axis coordinates of the interpolated points.
`y`	The y-axis coordinates of the interpolated points.

Santiago Barreda <sbarreda@ucdavis.edu>

http://en.wikipedia.org/wiki/Spline_interpolation

## generate ten random points
y = rnorm (10, 0, 5)
interpolate (y, show = TRUE)  ## plot a cubic interpolation
linear = interpolate (y, type = 'linear')   
## and compare to a linear interpolation
lines (linear, col = 2)