/**
 * Digital Filters Implementation
 *
 * Provides:
 * - Low-pass filter
 * - High-pass filter
 * - Band-pass filter
 * - Band-stop (notch) filter
 * - Butterworth filter
 * - Moving average (for smoothing)
 * - Savitzky-Golay filter
 */
export type FilterType = 'lowpass' | 'highpass' | 'bandpass' | 'bandstop';
export interface FilterOptions {
    /** Cutoff frequency in Hz (or normalized 0-1) */
    cutoff: number;
    /** Second cutoff for bandpass/bandstop filters */
    cutoffHigh?: number;
    /** Sample rate in Hz (default: 1.0 for normalized) */
    sampleRate?: number;
    /** Filter order (default: 2) */
    order?: number;
}
export interface ButterworthOptions extends FilterOptions {
    /** Filter type */
    type: FilterType;
}
export interface SingleFrequencyFilterOptions {
    /** Frequency to remove in Hz */
    frequency: number;
    /** Sampling rate in Hz */
    sampleRate: number;
    /** Bandwidth of the notch in Hz (default: 1.0) */
    bandwidth?: number;
}
/**
 * Apply a simple low-pass FIR filter
 */
export declare function lowPassFilter(data: Float32Array | Float64Array, cutoffHz: number, sampleRate: number, order?: number): Float32Array;
/**
 * Apply a simple high-pass FIR filter
 */
export declare function highPassFilter(data: Float32Array | Float64Array, cutoffHz: number, sampleRate: number, order?: number): Float32Array;
/**
 * Apply a band-pass FIR filter
 */
export declare function bandPassFilter(data: Float32Array | Float64Array, lowCutoffHz: number, highCutoffHz: number, sampleRate: number, order?: number): Float32Array;
/**
 * Apply a band-stop (notch) FIR filter
 */
export declare function bandStopFilter(data: Float32Array | Float64Array, lowCutoffHz: number, highCutoffHz: number, sampleRate: number, order?: number): Float32Array;
/**
 * Apply Butterworth filter (IIR)
 */
export declare function butterworth(data: Float32Array | Float64Array, options: ButterworthOptions): Float32Array;
/**
 * Apply a single frequency notch filter to remove periodic noise.
 * Implementing a 2nd order IIR notch filter.
 */
export declare function singleFrequencyFilter(data: Float32Array | Float64Array, options: SingleFrequencyFilterOptions): Float32Array;
/**
 * Exponential moving average filter
 */
export declare function exponentialMovingAverage(data: Float32Array | Float64Array, alpha?: number): Float32Array;
/**
 * Gaussian smoothing filter
 */
export declare function gaussianSmooth(data: Float32Array | Float64Array, sigma?: number): Float32Array;
/**
 * Savitzky-Golay smoothing filter
 */
export declare function savitzkyGolay(data: Float32Array | Float64Array, windowSize?: number, polynomialOrder?: number): Float32Array;
/**
 * Median filter (good for spike removal)
 */
export declare function medianFilter(data: Float32Array | Float64Array, windowSize?: number): Float32Array;