view src/app/spectrogram/MatrixUtils.ts @ 456:7bb0bac6f8dc

Add export button for recordings and option to remove audio item (also removes all related analyses atm). Revokes associated object url for audio on removal. Will be problematic if the history is used for undo / redo.

/**
 * 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;
}