Approx() and Approxfun() interpolation function

These functions return a list of points that linearly interpolates given data points, or a function performing the linear (or constant) interpolation.

Syntax: 

• approx   (x, y = NULL, xout, method = “linear”, n = 50,
            yleft, yright, rule = 1, f = 0, ties = mean)
• approxfun(x, y = NULL,       method = “linear”,
            yleft, yright, rule = 1, f = 0, ties = mean)

Parameters:

• x, y :numeric vectors giving the coordinates of the points to be interpolated.
• xout: an optional set of numeric values specifying where interpolation is to take place.
• method:specifies the interpolation method to be used. Choices are “linear” or “constant”.
• n:If xout is not specified, interpolation takes place at n equally spaced points spanning the interval [min(x), max(x)].
• yleft: the value to be returned when input x values are less than min(x). 
• yright: the value to be returned when input x values are greater than max(x).
• rule:an integer (of length 1 or 2) describing how interpolation is to take place outside the interval [min(x), max(x)].
• ties: handling of tied x values.

In this article, we will be looking towards the approx() and the aproxfun() interpolation function with working examples in the R Programming language.