view src/app/spectrogram/MatrixUtils.ts @ 394:f45a916eb5b1

Use the cross hair layer for notes, tracks and curve. This involved bodging in unit to ShapedFeatureData, which isn't particularly easy to do because this isn't an encapsulated type. Need to come back to improving this, as I am monkey-patching a unit property onto Arrays etc.

/**
 * Created by lucast on 23/05/2017.
 */

export function estimatePercentile(matrix, percentile) {
  // our sample is not evenly distributed across the whole data set:
  // it is guaranteed to include at least one sample from every
  // column, and could sample some values more than once. But it
  // should be good enough in most cases (todo: show this)
  if (matrix.length === 0) {
    return 0.0;
  }
  const w = matrix.length;
  const h = matrix[0].length;
  const n = w * h;
  const m = (n > 50000 ? 50000 : n); // should base that on the %ile
  let m_per = Math.floor(m / w);
  if (m_per < 1) {
    m_per = 1;
  }

  const sample = [];
  for (let x = 0; x < w; ++x) {
    for (let i = 0; i < m_per; ++i) {
      const y = Math.floor(Math.random() * h);
      const value = matrix[x][y];
      if (!isNaN(value) && value !== Infinity) {
        sample.push(value);
      }
    }
  }
  if (sample.length === 0) {
    return 0.0;
  }
  sample.sort((a, b) => { return a - b; });
  const ix = Math.floor((sample.length * percentile) / 100);
  const estimate = sample[ix];
  return estimate;
}