description:
Returns a pointer to the data in a specified column and row of the current data table of a data set.
Only the rows that are ``of interest'' are returned.
SDDS_table : Address of the SDDS_TABLE structure for the data set.
column_name : A NULL-terminated string giving the name of the column for which data is desired.
srow_index : Index of the row desired in the list of selected rows (or ``rows of interest'').
memory: Address of location into which to write the data. If NULL, memory
is allocated for this purpose.
return value:
On success, returns the address into which the data was placed. This pointer should
be cast to data-type*, where data-type is the data type of the columns selected.
Note that for type SDDS_STRING, data-type is char *.
On failure, returns NULL and records an error message.