Next: Arithmetic on datasets, Previous: Text files, Up: Gnuastro library [Contents][Index]
Tables are a collection of one dimensional datasets that are packed together into one file. They are the single most common format to store high-level (processed) information, hence they play a very important role in Gnuastro. For a more thorough introduction, please see Gnuastro’s Table. Gnuastro’s Table program, and all the other programs that can read from and write into tables, use the functions of this section. For a simple demonstration of using the constructs introduced here, see Library demo - reading and writing table columns.
Currently only plain text (see Gnuastro text table format) and FITS tables are supported by Gnuastro. However, the low-level table infra-structure is written such that for other formats are also possible and in future releases more formats will be supported, please let us know your priorities so they get higher priorities.
The default width and precision for generic types to use in writing numeric
types into a text file (plain text and FITS ASCII tables). When the dataset
doesn’t have any pre-set width and precision (see disp_width and
disp_precision in Generic data container (gal_data_t)) these will be
directly used in C’s printf command to write the number as a string.
The display format used in C’s printf to display data of different
types. The _STRING and _DECIMAL are unique for printing
strings and signed integers, they are mainly here for
completeness. However, unsigned integers and floating points can be
displayed in multiple formats:
For unsigned integers, it is possible to choose from _UDECIMAL
(unsigned decimal), _OCTAL (octal notation, for example 125
in decimal will be displayed as 175), and _HEX (hexadecimal
notation, for example 125 in decimal will be displayed as
7D).
For floating point, it is possible to display the number in _FLOAT
(floating point, for example 1500.345), _EXP (exponential,
for example 1.500345e+03), or _GENERAL which is the best of
the two for the given number.
All the current acceptable table formats to Gnuastro. The AFITS and
BFITS represent FITS ASCII tables and FITS Binary tables. You can
use these anywhere you see the tableformat variable.
When the desired column is not a number, these values determine if the
string to match, or regular expression to search, be in the name,
units or comments of the column meta data. These values
should be used for the searchin variables of the functions.
*filename, char *hdu, size_t *numcols, size_t *numrows, int *tableformat)Store the information of each column in a table (either as a text file or
as a FITS table) into an array of data structures with numcols
structures (one data structure for each column). The number of rows is
stored in the space that numrows points to. The format of the table
(e.g., ascii text file, or FITS binary or ASCII table) will be put in
tableformat (macros defined above). If the filename is not a FITS
file, then hdu will not be used (can be NULL).
Note that other than the character strings (column name, units and comments), nothing in the data structure(s) will be allocated by this function for the actual data (e.g., the ‘array’ or ‘dsize’ elements). This function is just for column information (meta-data), not column contents.
*allcols, size_t numcols, size_t numrows)This program will print the column information for all the columns (output
of gal_table_info). The output is in the same format as this command
with Gnuastro Table program (see Table):
$ asttable --info table.fits
*filename, char *hdu, gal_list_str_t *cols, int searchin, int ignorecase, int minmapsize)Read the specified columns in a text file (named filename) into a
linked list of data structures. If the file is FITS, then hdu will
also be used, otherwise, hdu is ignored.
The information to search for columns should be specified by the
cols list of strings (see List of strings). The string in each
node of the list may be a number, an exact match to a column name, or a
regular expression (in GNU AWK format) enclosed in / /. The
searchin value must be one of the macros defined above. If
cols is NULL, then this function will read the full table.
The output is an individually allocated list of datasets (see List of gal_data_t) with the same order of the cols list. Note that one
column node in the cols list might give multiple columns (for
example from regular expressions), in this case, the order of output
columns that correspond to that one input, are in order of the table (which
column was read first). So the first requested column is the first popped
data structure and so on.
**comments, char *program_string, time_t *rawtime)Add some basic information to the list of comments. This basic
information includes the following information
COMMIT in Output headers).
rawtime (time_t is C’s
calendar time format defined in time.h). You can calculate the time
in this format with the following expressions:
time_t rawtime; time(&rawtime);
program_string. If it is NULL,
this line is ignored.
*cols, gal_list_str_t *comments, int tableformat, char *filename, int dontdelete)Write the cols list of datasets into a table in filename (see
List of gal_data_t). The format of the table can be determined with
tableformat that accepts the macros defined above. If
comments!=NULL, then the list of comments will also be printed into
the output table. When the output table is a plain text file, each node’s
string will be printed after a # (so it can be considered as a
comment). If filename already exists and dontdelete is not
zero, this function will abort the program with an error.
*logll, char *program_string, time_t *rawtime, gal_list_str_t *comments, char *filename, int dontdelete, int quiet)Write the logll list of datasets into a table in filename
(see List of gal_data_t). This function is just a wrapper around
gal_table_comments_add_intro and gal_table_write (see
above). If quiet is non-zero, this function will print a message
saying that the filename has been created.
Next: Arithmetic on datasets, Previous: Text files, Up: Gnuastro library [Contents][Index]
GNU Astronomy Utilities 0.4 manual, September 2017.