improve standardizeMissing.m

[AvanishSalunke]

1. If an unsupported type is passed, octave will ignore it and return the input unchanged.

octave:4> standardizeMissing ({'abc', 1}, 1)
ans =
  1x2 cell array

    {'abc'}    {[1]}    

octave:5> standardizeMissing ({'abc', 1}, 3)
ans =
  1x2 cell array

    {'abc'}    {[1]}    

2. For indicators in numeric , it just checked whether the indicators are numeric are not.

octave:6> standardizeMissing (int8 ([1, 2, 3]), int16 (2))
ans =

  1  2  3

matlab

>> standardizeMissing (int8 ([1, 2, 3]), int16 (2))
Error using matlab.internal.math.ismissingKernel>arraySwitchIndicators (line 164)
Second argument must be int8 or double.

Error in matlab.internal.math.ismissingKernel (line 40)
        IA = arraySwitchIndicators(A,false,indstruct,stdize);
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error in standardizeMissing (line 15)
    B = matlab.internal.math.ismissingKernel(A,indicators,true);
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

3. check for logical arrays has been added.

One thing that is not handled in this PR is how this function handles categorical array while using a char indicator,
For eg:
in octave:

octave:18>  A = categorical ({'a', 'b', 'c'});
octave:19>  indicator = 'b';
octave:20> standardizeMissing (A , indicator)
ans =
  1x3 categorical array

    <undefined>    b    c  

in matlab:

>> A = categorical ({'a', 'b', 'c'});
>> indicator = 'b';
>> standardizeMissing (A , indicator)

ans = 

  1×3 categorical array

     a      <undefined>      c 

the possible reason for it can be since isordinal function is not yet implemented in octave.
(my version is 11.0.0)

octave:21> ismember (A, indicator)
error: 'isordinal' undefined near line 1069, column 32

The ‘isordinal’ function is not yet implemented in Octave.

Please read <https://www.octave.org/missing.html> to learn how you can
contribute missing functionality.
error: called from
    ismember at line 1069 column 15