Table of contents
CSPICE_EKGD returns an element of double precision 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:
[ ddata, null, found] = cspice_ekgd( selidx, row, elment )
returns:
ddata the value of the requested element at data location
'selidx', 'row', 'elment'.
[1,1] = size(ddata); double = class(ddata)
null a boolean indicating if 'ddata' 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 these examples 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 PLATFORM_CLOCK values (double precision)
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 ekgd_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 'PLATFORM_CLOCK'
% of double precision values.
%
% Define a set of constraints to perform a query on all
% loaded EK files (the SELECT clause). In this case select
% the column 'PLATFORM_CLOCK' from table 'VIKING_SEDR_DATA'
% sorted by 'IMAGE_NUMBER'.
%
query = ['Select PLATFORM_CLOCK 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 double precision 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_ekgd to retrieve the value from
% row/column position.
%
[ddata, isnull, found] = cspice_ekgd( selidx, rowno, eltidx );
%
% Output the value, if non-null data exist at the
% requested position.
%
if ~isnull
fprintf( 'Row %3d: Double precision data: %f\n', rowno, ...
ddata );
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: Double precision data: 119.880000
Row 2: Double precision data: 119.270000
Row 3: Double precision data: 119.880000
Row 4: Double precision data: 119.270000
Row 5: Double precision data: 119.880000
Row 6: Double precision data: 119.270000
Row 7: Double precision data: 120.140000
Row 8: Double precision data: 119.520000
Row 9: Double precision data: 120.140000
Row 10: Double precision data: 120.140000
Row 11: Double precision data: 120.140000
Row 12: Double precision data: 221.920000
Row 13: Double precision data: 221.920000
Row 14: Double precision data: 221.920000
Row 15: Double precision data: 120.140000
Row 16: Double precision data: 120.140000
Row 17: Double precision data: 120.140000
Row 18: Double precision data: 120.220000
Row 19: Double precision data: 120.220000
Row 20: Double precision data: 120.220000
Row 21: Double precision data: 120.370000
Row 22: Double precision data: 120.370000
Row 23: Double precision data: 120.370000
Row 24: Double precision data: 120.290000
Row 25: Double precision data: 120.290000
Row 26: Double precision data: 120.290000
2) 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_TIME values (double
precision time) 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
Use the LSK kernel below to load the leap seconds and time
constants required for the conversions.
naif0012.tls
Example code begins here.
function ekgd_ex2()
%
% Assign an EK file to load.
%
EK = 'vo_sedr.bdb';
LSKNAM = 'naif0012.tls';
%
% Load leapseconds file for time conversion.
%
cspice_furnsh( LSKNAM );
%
% Load the EK.
%
cspice_furnsh( EK )
%
% The table 'VIKING_SEDR_DATA' has a column 'IMAGE_TIME'
% of double precision 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_TIME' from table 'VIKING_SEDR_DATA'
% sorted by 'IMAGE_NUMBER'.
%
query = ['Select IMAGE_TIME 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 double precision 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_ekgd to retrieve the value from
% row/column position.
%
[ddata, isnull, found] = cspice_ekgd( selidx, rowno, eltidx );
%
% Output the value, if non-null data exist at the
% requested position.
%
if ~isnull
[utcstr] = cspice_et2utc( ddata, 'C', 3 );
fprintf( 'Row %3d: Time data: %s\n', rowno, utcstr );
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: Time data: 1976 JUN 16 16:50:55.925
Row 2: Time data: 1976 JUN 16 16:51:00.269
Row 3: Time data: 1976 JUN 16 20:56:53.051
Row 4: Time data: 1976 JUN 16 20:56:57.395
Row 5: Time data: 1976 JUN 17 01:02:50.177
Row 6: Time data: 1976 JUN 17 01:02:54.521
Row 7: Time data: 1976 JUN 17 05:08:56.263
Row 8: Time data: 1976 JUN 17 05:09:00.607
Row 9: Time data: 1976 JUN 17 06:30:28.424
Row 10: Time data: 1976 JUN 17 06:30:46.174
Row 11: Time data: 1976 JUN 17 06:30:55.168
Row 12: Time data: 1976 JUN 17 11:17:47.471
Row 13: Time data: 1976 JUN 17 11:18:05.221
Row 14: Time data: 1976 JUN 17 11:18:14.215
Row 15: Time data: 1976 JUN 17 13:20:23.634
Row 16: Time data: 1976 JUN 17 13:20:41.384
Row 17: Time data: 1976 JUN 17 13:20:50.378
Row 18: Time data: 1976 JUN 17 15:23:17.717
Row 19: Time data: 1976 JUN 17 15:23:35.467
Row 20: Time data: 1976 JUN 17 15:23:44.461
Row 21: Time data: 1976 JUN 17 17:26:20.760
Row 22: Time data: 1976 JUN 17 17:26:38.510
Row 23: Time data: 1976 JUN 17 17:26:47.504
Row 24: Time data: 1976 JUN 17 19:29:23.803
Row 25: Time data: 1976 JUN 17 19:29:41.553
Row 26: Time data: 1976 JUN 17 19:29:50.547
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 double precision data
and "val_42" containing a vector of K doubles.
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 DP or TIME 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 example's EK. Updated example
code to work with provided EK, and added additional examples.
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 double precision column entry
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