Table of contents
CSPICE_EKGI returns an element of integer data from a
specified row in a specified column of the set of rows matching
the previous cspice_ekfind SELECT query.
Given:
selidx the index for a column of interest satisfying the SELECT
clause, the column indices range from 1 to number of
columns in the SELECT clause.
[1,1] = size(selidx); int32 = class(selidx)
row the index for a row in the column identified by 'selidx',
the column indices range from 1 to 'nmrows' where 'nmrows'
equals the total number of rows satisfying the SELECT clause.
[1,1] = size(row); int32 = class(row)
elment the index for an element of the data at the 'selidx','row'
position; a scalar value at 'selidx', 'row' has 'elment'
value one.
[1,1] = size(elment); int32 = class(elment)
the call:
[idata, null, found] = cspice_ekgi( selidx, row, elment )
returns:
idata the value of the requested element at data location
'selidx', 'row', 'elment'.
[1,1] = size(idata); int32 = class(idata)
null a boolean indicating if 'idata' has a null value.
[1,1] = size(null); logical = class(null)
found a boolean indicating whether the specified value at
'selidx', 'row', 'elment' was found.
[1,1] = size(found); logical = class(found)
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
and the machine specific arithmetic implementation.
1) Perform a query on an EK file that contains a database with
the Supplementary Engineering Data Records of the Viking Project
in order to retrieve the IMAGE_NUMBER values (integer numbers)
that correspond to the images with IMAGE_NUMBER smaller than
a given value, ordered by IMAGE_NUMBER.
Use the EK kernel below to load the information from the
original Supplementary Engineering Data Record (SEDR) data
set generated by the Viking Project.
vo_sedr.bdb
Example code begins here.
function ekgi_ex1()
%
% Assign an EK file to load..
%
EK = 'vo_sedr.bdb';
%
% Load the EK.
%
cspice_furnsh( EK )
%
% The table 'VIKING_SEDR_DATA' has a column 'IMAGE_NUMBER'
% of integer values.
%
% Define a set of constraints to perform a query on all
% loaded EK files (the SELECT clause). In this case select
% the column 'IMAGE_NUMBER' from table 'VIKING_SEDR_DATA'
% sorted by 'IMAGE_NUMBER'.
%
query = ['Select IMAGE_NUMBER from VIKING_SEDR_DATA ' ...
'where IMAGE_NUMBER < 25860000 order by IMAGE_NUMBER'];
%
% Query the EK system for data rows matching the
% SELECT constraints.
%
[nmrows, error, errmsg] = cspice_ekfind( query );
%
% Check whether an error occurred while processing the
% SELECT clause. If so, output the error message.
%
if ( error )
printf( 'SELECT clause error: %s\n', errmsg );
end
%
% Loop over each row found matching the query.
%
for rowno = 1:nmrows
%
% Fetch the integer data. We know the query returned
% one column and the column contains only scalar data,
% so the index of all elements is 1.
%
selidx = 1;
eltidx = 1;
%
% Use cspice_ekgi to retrieve the value from
% row/column position.
%
[idata, isnull, found ] = cspice_ekgi( selidx, ...
rowno, ...
eltidx );
%
% Output the value, if non-null data exist at the
% requested position.
%
if ~isnull
fprintf( 'Row %3d: Integer data: %d\n', rowno, idata );
end
end
%
% Clear the kernel pool and database. Note, you don't normally
% unload an EK after a query, rather at the end of a program.
%
cspice_kclear
When this program was executed on a Mac/Intel/Octave6.x/64-bit
platform, the output was:
Row 1: Integer data: 25837050
Row 2: Integer data: 25837051
Row 3: Integer data: 25840344
Row 4: Integer data: 25840345
Row 5: Integer data: 25843638
Row 6: Integer data: 25843639
Row 7: Integer data: 25846934
Row 8: Integer data: 25846935
Row 9: Integer data: 25848026
Row 10: Integer data: 25848030
Row 11: Integer data: 25848032
Row 12: Integer data: 25851874
Row 13: Integer data: 25851878
Row 14: Integer data: 25851880
Row 15: Integer data: 25853516
Row 16: Integer data: 25853520
Row 17: Integer data: 25853522
Row 18: Integer data: 25855162
Row 19: Integer data: 25855166
Row 20: Integer data: 25855168
Row 21: Integer data: 25856810
Row 22: Integer data: 25856814
Row 23: Integer data: 25856816
Row 24: Integer data: 25858458
Row 25: Integer data: 25858462
Row 26: Integer data: 25858464
Suppose a SELECT clause return data consisting of three columns (N=3)
and four rows (M=4):
col 1 col 2 col 3
row 1 val_11 val_12 val_13
row 2 val_21 val_22 val_23
row 3 val_31 val_32 val_33
row 4 val_41 val_42 val_43
with "col 2" and "col 3" containing scalar integer data and "val_42"
containing a vector of K integers.
Retrieving the data elements depends on the values for the index set
"selidx," "row," and "elment."
Use the set
'selidx' = 2, 'row' = 3, 'elment' = 1
to fetch scalar "val_32."
Use the set
'selidx' = 3, 'row' = 4, 'elment' = 1
to fetch scalar "val_43."
Use the set
'selidx' = 2, 'row' = 4, 'elment' = K
to fetch the final element of vector "val_42"
`elment' is allowed to exceed the number of elements in the column
entry; if it does, `found' returns as false. This allows the caller
to read data from the column entry in a loop without checking the
number of available elements first.
1) If the input argument `elment' is less than 1, the error
SPICE(INVALIDINDEX) is signaled by a routine in the call tree
of this routine and `found' is returned false. However, `elment'
is allowed to be greater than the number of elements in the
specified column entry; this allows the caller to read data
from the column entry in a loop without checking the number of
available elements first. If `elment' is greater than the number
of available elements, `found' is returned false.
2) If `selidx' is outside of the range established by the last query
passed to the EK search engine, the error SPICE(INVALIDINDEX) is
signaled by a routine in the call tree of this routine and `found' is
returned false.
3) If the input argument `row' is less than 1 or greater than the
number of rows matching the query, the error
SPICE(INVALIDINDEX) is signaled by a routine in the call tree
of this routine and `found' is returned false.
4) If the specified column does not have integer type, the error
SPICE(INVALIDTYPE) is signaled by a routine in the call tree
of this routine.
5) If this routine is called when no E-kernels have been loaded,
the error SPICE(NOLOADEDFILES) is signaled by a routine in the
call tree of this routine.
6) If any of the input arguments, `selidx', `row' or `elment', is
undefined, an error is signaled by the Matlab error handling
system.
7) If any of the input arguments, `selidx', `row' or `elment', is
not of the expected type, or it does not have the expected
dimensions and size, an error is signaled by the Mice
interface.
This routine reads binary "sequence component" EK files.
In order for a binary EK file to be accessible to this routine,
the file must be "loaded" via a call to the routine cspice_furnsh.
Text format EK files cannot be used by this routine; they must
first be converted by binary format by the NAIF Toolkit utility
SPACIT.
None.
MICE.REQ
EK.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Mice Version 1.3.0, 10-AUG-2021 (EDW) (JDR)
Edited the -Examples section to comply with NAIF standard. Added
example's problem statement and and example's EK. Updated example
code to work with provided EK.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections.
Eliminated use of "lasterror" in rethrow.
Removed reference to the function's corresponding CSPICE header from
-Required_Reading section.
-Mice Version 1.2.1, 03-NOV-2014 (EDW)
Edited -I/O section to conform to NAIF standard for Mice
documentation.
-Mice Version 1.2.0, 10-MAY-2011 (EDW)
"logical" call replaced with "zzmice_logical."
-Mice Version 1.0.0, 10-APR-2010 (EDW)
fetch element from integer column entry
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