Simple matrix transposition

transpose.js

const R = require('ramda');
const mapIndexed = R.addIndex(R.map);

// transpose :: [[a]] -> [[a]] -- (row, col) becomes (col, row)
const transpose = function(matrix) {
  return mapIndexed(function (_, col) {
    return R.reject(R.isNil, R.map(R.prop(col), matrix));
  }, R.head(matrix));
};

// transpose([[1, 2, 3], [4, 5, 6], [7. 8]]); //=> [[1, 4, 7], [2, 5, 8], [3, 6]]