dev@343: /**
dev@343:  * Created by lucast on 23/05/2017.
dev@343:  */
dev@343: 
dev@343: export function estimatePercentile(matrix, percentile) {
dev@343:   // our sample is not evenly distributed across the whole data set:
dev@343:   // it is guaranteed to include at least one sample from every
dev@343:   // column, and could sample some values more than once. But it
dev@343:   // should be good enough in most cases (todo: show this)
dev@343:   if (matrix.length === 0) {
dev@343:     return 0.0;
dev@343:   }
dev@343:   const w = matrix.length;
dev@343:   const h = matrix[0].length;
dev@343:   const n = w * h;
dev@343:   const m = (n > 50000 ? 50000 : n); // should base that on the %ile
dev@343:   let m_per = Math.floor(m / w);
dev@343:   if (m_per < 1) {
dev@343:     m_per = 1;
dev@343:   }
dev@343: 
dev@343:   const sample = [];
dev@343:   for (let x = 0; x < w; ++x) {
dev@343:     for (let i = 0; i < m_per; ++i) {
dev@343:       const y = Math.floor(Math.random() * h);
dev@343:       const value = matrix[x][y];
dev@343:       if (!isNaN(value) && value !== Infinity) {
dev@343:         sample.push(value);
dev@343:       }
dev@343:     }
dev@343:   }
dev@343:   if (sample.length === 0) {
dev@343:     return 0.0;
dev@343:   }
dev@343:   sample.sort((a, b) => { return a - b; });
dev@343:   const ix = Math.floor((sample.length * percentile) / 100);
dev@343:   const estimate = sample[ix];
dev@343:   return estimate;
dev@343: }