Documentation

polyline.rdp() function

polyline.rdp() is experimental and subject to change at any time.

polyline.rdp() applies the Ramer Douglas Peucker (RDP) algorithm to input data to downsample curves composed of line segments into visually indistinguishable curves with fewer points.

Function type signature
(
    <-tables: stream[A],
    ?epsilon: float,
    ?retention: float,
    ?timeColumn: string,
    ?valColumn: string,
) => stream[B] where A: Record, B: Record
For more information, see Function type signatures.

Parameters

valColumn

Column with Y axis values of the given curve. Default is _value.

timeColumn

Column with X axis values of the given curve. Default is _time.

epsilon

Maximum tolerance value that determines the amount of compression.

Epsilon should be greater than 0.0.

retention

Percentage of points to retain after downsampling.

Retention rate should be between 0.0 and 100.0.

tables

Input data. Default is piped-forward data (<-).

Examples

Downsample data using the RDP algorithm

When using polyline.rdp(), leave both epsilon and retention unspecified to automatically calculate the maximum tolerance for producing a visually indistinguishable curve.

import "experimental/polyline"

data
    |> polyline.rdp()

View example input and ouput

Downsample data using the RDP algorithm with an epsilon of 1.5

import "experimental/polyline"

data
    |> polyline.rdp(epsilon: 1.5)

View example input and ouput

Downsample data using the RDP algorithm with a retention rate of 90%

import "experimental/polyline"

data
    |> polyline.rdp(retention: 90.0)

View example input and ouput


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