#### 8.2.6.6 categorical.double ¶

Method: `out =` double `(obj)` ¶

  Convert to double array, by getting the underlying code values.

  Converts obj to a string array. The doubles will be the underlying numeric code values of obj, or `NaN` for undefined values.

  The numeric code values of two different categorical arrays do *not* necessarily correspond to the same string values, and can *not* be meaningfully compared for equality or ordering.

  Returns a `double` array the same size as obj.