Function reduceMatrix

src/heatmap.ts:210–234

(matrix: number[][], factor: number)

}  // Close class HeatMap.

export function reduceMatrix(matrix: number[][], factor: number): number[][] {
  if (matrix.length !== matrix[0].length) {
    throw new Error("The provided matrix must be a square matrix");
  }
  if (matrix.length % factor !== 0) {
    throw new Error("The width/height of the matrix must be divisible by " +
        "the reduction factor");
  }
  let result: number[][] = new Array(matrix.length / factor);
  for (let i = 0; i < matrix.length; i += factor) {
    result[i / factor] = new Array(matrix.length / factor);
    for (let j = 0; j < matrix.length; j += factor) {
      let avg = 0;
      // Sum all the values in the neighborhood.
      for (let k = 0; k < factor; k++) {
        for (let l = 0; l < factor; l++) {
          avg += matrix[i + k][j + l];
        }
      }
      avg /= (factor * factor);
      result[i / factor][j / factor] = avg;
    }
  }
  return result;
}