this.rows = rows;

  this.cols = cols;

  this.matrix = new Array(rows);

  for (var i = 0; i < this.rows; i++) {

    this.matrix[i] = new Array(cols);

    for (var j = 0; j < this.cols; j++) {

      this.matrix[i][j] = 0;

    }

  }

}

​

// This fills the matrix with random values (gaussian distribution)

Matrix.prototype.randomize = function() {

  for (var i = 0; i < this.rows; i++) {

    for (var j = 0; j < this.cols; j++) {

      this.matrix[i][j] = randomGaussian();

      //this.matrix[i][j] = random(-1, 1);

    }

  }

}

​

// Take the matrix and make it a 1 dimensional array

Matrix.prototype.toArray = function() {

  // Add all the values to the array

  var arr = [];

  for (var i = 0; i < this.rows; i++) {

    for (var j = 0; j < this.cols; j++) {

      arr.push(this.matrix[i][j]);

    }

  }

  return arr;

}

​

​

// This transposes a matrix

// rows X cols --> cols X rows

Matrix.prototype.transpose = function() {

  var result = new Matrix(this.cols, this.rows);

  for (var i = 0; i < result.rows; i++) {

    for (var j = 0; j < result.cols; j++) {

      result.matrix[i][j] = this.matrix[j][i];

    }

  }

  return result;

}

​

// This makes a copy of the matrix

Matrix.prototype.copy = function() {

  var result = new Matrix(this.rows, this.cols);

  for (var i = 0; i < result.rows; i++) {

    for (var j = 0; j < result.cols; j++) {

      result.matrix[i][j] = this.matrix[i][j];

    }

  }

  return result;

}

​

// This adds another matrix or a single value

Matrix.prototype.add = function(other) {

  // Are we trying to add a Matrix?

  if (other instanceof Matrix) {

    for (var i = 0; i < this.rows; i++) {

      for (var j = 0; j < this.cols; j++) {

        this.matrix[i][j] += other.matrix[i][j];

      }

    }

    // Or just a single scalar value?

  } else {

    for (var i = 0; i < this.rows; i++) {

      for (var j = 0; j < this.cols; j++) {

        this.matrix[i][j] += other;

      }

    }

  }

}

​

// This multiplies another matrix or a single value

// This is different than the dot() function!

Matrix.prototype.multiply = function(other) {

  // Are we trying to multiply a Matrix?

  if (other instanceof Matrix) {

    for (var i = 0; i < this.rows; i++) {

      for (var j = 0; j < this.cols; j++) {

        this.matrix[i][j] *= other.matrix[i][j];

      }

    }

    // Or just a single scalar value?

  } else {

    for (var i = 0; i < this.rows; i++) {

      for (var j = 0; j < this.cols; j++) {

        this.matrix[i][j] *= other;

      }

    }

  }

}

​

​

// These are some static functions to operate on a matrix

​

// This is the trickiest one

// Takes a function and applies it to all values in the matrix

Matrix.map = function(m, fn) {

  var result = new Matrix(m.rows, m.cols);

  for (var i = 0; i < result.rows; i++) {

    for (var j = 0; j < result.cols; j++) {

      result.matrix[i][j] = fn(m.matrix[i][j]);

    }

  }

  return result;

}

​

// Subtracts one matrix from another

Matrix.subtract = function(a, b) {

  var result = new Matrix(a.rows, a.cols);

  for (var i = 0; i < result.rows; i++) {

    for (var j = 0; j < result.cols; j++) {

      result.matrix[i][j] = a.matrix[i][j] - b.matrix[i][j];

    }

  }

  return result;

}

​

​

// Multiplies two matrices together

Matrix.dot = function(a, b) {

  // Won't work if columns of A don't equal columns of B

  if (a.cols != b.rows) {

    console.log("Incompatible matrix sizes!");

    return;

  }

  // Make a new matrix

  var result = new Matrix(a.rows, b.cols);

  for (var i = 0; i < a.rows; i++) {

    for (var j = 0; j < b.cols; j++) {

      // Sum all the rows of A times columns of B

      var sum = 0;

      for (var k = 0; k < a.cols; k++) {

        sum += a.matrix[i][k] * b.matrix[k][j];

      }

      // New value

      result.matrix[i][j] = sum;

    }

  }

  return result;

}

​

​

// Turn a 1 dimensional array into a matrix

Matrix.fromArray = function(array) {

  var m = new Matrix(array.length, 1);

  for (var i = 0; i < array.length; i++) {

    m.matrix[i][0] = array[i];

  }

  return m;

}

​

// Visualize the matrix in the browser window

// if idSelector is passed, the matrix is displayed in the table with the given id

Matrix.prototype.visualize = function(idSelector) {

  let table;

  if (idSelector) {

    if (typeof idSelector !== 'string') {

      console.error('Invalid argument type (expected string, received ' + typeof idSelector + ')');

      return;

    }

    // select table by id, otherwise create new table if not exists

    table = document.getElementById(idSelector);

    if (table === null) {

      table = document.createElement('table');

      table.id = idSelector;

      document.body.appendChild(table);

    }

    table.innerHTML = ''; // clear

    table.setAttribute('title', 'id: ' + idSelector);

  } else {

    // append table without id to body

    table = document.createElement('table');

    document.body.appendChild(table);

  }

  table.className = 'vis-matrix';

  table.style.margin = '40px';

  table.style.padding = '4px 10px';

  table.style.borderLeft = '2px solid black';

  table.style.borderRight = '2px solid black';

  table.style.borderRadius = '20px';

  this.matrix.forEach((el, iRow) => {

    let row = document.createElement('tr');

    el.forEach((el, iCol) => {

      let cell = document.createElement('td');

      cell.innerHTML = el;

      cell.setAttribute('title', '[' + iRow + ',' + iCol + ']');

      cell.style.padding = '3px 8px';

      cell.style.textAlign = 'center';

      cell.style.color = 'black';

      row.appendChild(cell);

    })

    table.appendChild(row);

  });

}

​

Matrix.prototype.pprint = function(){ //"pretty print" the matrix

  let fstring = '['; 

  for (let i=0;i<this.matrix.length;i++){

    fstring +=  (i!=0?' ':'') + ` [${this.matrix[i].map(x=>' ' + x.toString() + ' ')}],\n`;

  }

  console.log(fstring.substring(0,fstring.length-2) + ' ]');

}