description: Returns an array of double-precision values containing the data in a specified column, provided
the column contains numerical data. Integer data types are properly cast to double precision.
SDDS_table: Address of the SDDS_TABLE structure for the data set.
column_name: A NULL-terminated character string giving the name of the column
for which data is desired.
return value: On success, returns the address of a newly-allocated array of double’s containing the data. On
failure, returns NULL and records an error message.