standardizeMissing
              Replace data values specified by indicator in A by the standard ’missing’ data value for that data type.
A can be a numeric scalar or array, a character vector or array, or a cell array of character vectors (a.k.a. string cells).
indicator can be a scalar or an array containing values to be replaced by the ’missing’ value for the class of A, and should have a data type matching A.
’missing’ values are defined as :
NaN: single, double
 " " (white space): char
 {""} (empty string in cell): string cells.
 Compatibility Notes:
standardizeMissing
 does not restrict indicator of type char to row vectors.
 single and double have defined ’missing’
 values, so A of other data types will always output
 B = A.
 See also: fillmissing, ismissing, rmmissing
Source Code: standardizeMissing