polyline.rdp() function

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

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
• Downsample data using the RDP algorithm with an epsilon of 1.5
• Downsample data using the RDP algorithm with a retention rate of 90%

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()

Downsample data using the RDP algorithm with an epsilon of 1.5

import "experimental/polyline"

data
    |> polyline.rdp(epsilon: 1.5)

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

import "experimental/polyline"

data
    |> polyline.rdp(retention: 90.0)