code: function add(arr, arg) {
      // check if arg is a vector or scalar
      if (isUsable(arg)) {
        if (!isUsable(arg[0])) arg = [ arg ];
        return jStat.map(arr, function(value, row, col) {
          return value + arg[row][col];
        });
      }
      return jStat.map(arr, function(value) { return value + arg; });
    }
docs: add a vector/matrix to a vector/matrix or scalar