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EWMA Filter (ewma)

Exponentially Weighted Moving Average filter, a single-pole low-pass filter that smooths values by blending new samples with the previous average.

Update formula: avg = weight * value + (1 - weight) * last

Data Structure​

struct ewma_filter_t {
    float weight;
    float last;
};

API​

struct ewma_filter_t * ewma_alloc(float weight);
void ewma_free(struct ewma_filter_t * filter);
float ewma_update(struct ewma_filter_t * filter, float value);
void ewma_clear(struct ewma_filter_t * filter);
  • ewma_alloc — Allocate filter, weight range 0~1, higher values track new samples more closely
  • ewma_free — Free filter
  • ewma_update — Input new value, returns updated average
  • ewma_clear — Reset filter state

Example​

Sensor Data Filtering​

struct ewma_filter_t * f = ewma_alloc(0.2f);

while(running)
{
    float sample = read_sensor();
    float filtered = ewma_update(f, sample);
}

ewma_free(f);

Reset Filter​

ewma_clear(f);