function _vectorNormPlusInfinity (x) {
      // norm(x, Infinity) = max(abs(x))
      let pinf = 0
      // skip zeros since abs(0) === 0
      x.forEach(function (value) {
        const v = abs(value)
        if (larger(v, pinf)) {
          pinf = v
        }
      }, true)
      return pinf
    }
Calculate the plus infinity norm for a vector
@param {Matrix} x
@returns {number} Returns the norm
@private