Interpolation

This library implements the interpolation methods described here http://paulbourke.net/miscellaneous/interpolation/.

When loaded, the following extension is provided

ext-interpolate

(ext-interpolate value table optMethod)

Where value is the x-position in the table, table is the interpolation table and optMethod is an optional argument that specifies the interpolation method to use (by default it uses Catmull-Rom splines).

The available methods are:

0. Linear
1. Cosine
2. Cubic splines
3. Catmull-Rom splines (recommended)

Note: Outside of the table all points are set to the same value as the last point in the table.

Example

(import "pkg::interpolation@://vesc_packages/lib_interpolation/interpolation.vescpkg" 'interpolation)

(load-native-lib interpolation)

(def int-tab '(
        (-500.0 90.0)
        (0.0 80.0)
        (500.0 82.0)
        (1000.0 90.0)
        (1500.0 94.0)
        (3000.0 96.0)
        (5000.0 100.0)
))

(ext-interpolate 1220 int-tab 3)
> {92.216660}

Example: Plotting

(import "pkg::interpolation@://vesc_packages/lib_interpolation/interpolation.vescpkg" 'interpolation)

(load-native-lib interpolation)

(def int-tab '(
        (-500.0 90.0)
        (0.0 80.0)
        (500.0 82.0)
        (1000.0 90.0)
        (1500.0 94.0)
        (1960.0 80.6)
        (3000.0 96.0)
        (5000.0 100.0)
))

(plot-init "Val" "Output")
(plot-add-graph "Linear")
(plot-add-graph "Cosine")
(plot-add-graph "Cubic")
(plot-add-graph "Catmull-Rom")

(looprange i 0 4
    (progn
        (plot-set-graph i)
        (loopfor j -1000 (< j 7000) (+ j 10)
            (plot-send-points j (ext-interpolate j int-tab i))
)))