StreamingLowess API

See also: fastLowess

When to Use

• Dataset >100,000 points
• Memory-constrained environments
• Batch processing pipelines

Class

StreamingLowess

The StreamingLowess class processes data in chunks, suitable for very large datasets or streaming applications.

Constructor:

const { StreamingLowess } = require('fastlowess-wasm');

const stream = new StreamingLowess({ fraction: 0.5 }, { chunk_size: 50, overlap: 10 });
console.log("typeof process_chunk:", typeof stream.process_chunk);

typeof process_chunk: function

• options: An object containing LowessOptions fields.
• streamingOptions: An object containing StreamingOptions fields.

Methods:

const { StreamingLowess } = require('fastlowess-wasm');

const n = 100;
const x = Float64Array.from({ length: n }, (_, i) => i * 2 * Math.PI / (n - 1));
const y = Float64Array.from(x, xi => Math.sin(xi) + 0.1);

const stream = new StreamingLowess({ fraction: 0.5 }, { chunk_size: 50, overlap: 10 });
const partialResult = stream.process_chunk(x.slice(0, 50), y.slice(0, 50));
console.log("Fraction used:", partialResult.fraction_used);

Fraction used: 0.5

• Processes a chunk of data. Returns partial results.

const { StreamingLowess } = require('fastlowess-wasm');

const n = 100;
const x = Float64Array.from({ length: n }, (_, i) => i * 2 * Math.PI / (n - 1));
const y = Float64Array.from(x, xi => Math.sin(xi) + 0.1);

const stream = new StreamingLowess({ fraction: 0.5 }, { chunk_size: 50, overlap: 10 });
stream.process_chunk(x.slice(0, 50), y.slice(0, 50));
stream.process_chunk(x.slice(50), y.slice(50));
const finalResult = stream.finalize();
console.log("Fraction used:", finalResult.fraction_used);

Fraction used: 0.5

• Finalizes the smoothing process and returns any remaining buffered results.

Result Structure

LowessResult

Returned by process_chunk() and finalize().

Field	Type	Description
x	Float64Array	Sorted x values
y	Float64Array	Smoothed y values
fraction_used	number	Fraction used
iterations_used	number | undefined	Robustness iterations actually performed
residuals	Float64Array | undefined	Residuals (if return_residuals)
robustness_weights	Float64Array | undefined	Robustness weights (if return_robustness_weights)
diagnostics	Diagnostics | undefined	Fit metrics (if return_diagnostics)
dimensions	number	Number of predictor dimensions

See wasm.md for the full LowessResult field reference.

Options Structure

StreamingOptions (inherits LowessOptions)

Field	Type	Default	Description
chunk_size	number	5000	Data chunk size
overlap	number	500	Overlap between chunks
merge_strategy	string	"weighted_average"	Strategy for blending overlap regions

Options

merge_strategy

See: Merge Strategies

Strategy	Alias	Behavior
"weighted_average" (default)	"weighted"	Distance-weighted blend
"average"	"mean"	Average overlapping values
"take_first"	"first"	Keep left chunk values
"take_last"	"last"	Keep right chunk values

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Always call finalize()

The streaming adapter buffers overlap data. Call finalize() after the last chunk to retrieve the buffered tail.