[gnuastro-commits] master dea74348: Book: suggestion to use the -s option of seq with many columns

[Mohammad Akhlaghi]

branch: master
commit dea7434859d678b4be0b3662f895cc653fee1db1
Author: Zohreh-Ghaffari <zoh.ghaffari@gmail.com>
Commit: Mohammad Akhlaghi <mohammad@akhlaghi.org>

    Book: suggestion to use the -s option of seq with many columns
    
    Until now, the '_all' option has proven invaluable for appending columns at
    either end of a table, situations arise where the task is to selectively
    delete or retain specific columns within a table, particularly when the
    table contains numerous columns. In such cases, generating a sequence of
    the desired columns becomes necessary.
    
    With this commit, an explanation has been added into the Gnuastro book for
    such cases. This addition outlines the methodology to create a sequence
    encompassing an arbitrary sequence of column numbers using the 'seq'
    command. By utilizing the '-s' flag, a comma delimiter is effectively
    inserted between each column number, rendering it suitable for the '-c'
    option in the Table program.
---
 doc/gnuastro.texi | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/doc/gnuastro.texi b/doc/gnuastro.texi
index bfe56e2c..6fcfcd06 100644
--- a/doc/gnuastro.texi
+++ b/doc/gnuastro.texi
@@ -3872,6 +3872,18 @@ $ asttable three-in-one-3.fits -ocolor-cat.fits 
-c1,2,RA,DEC \
 $ asttable color-cat.fits -i
 @end example
 
+Sometimes, because of a particular way of storing data, you might need to take 
all input columns.
+If there are many columns (for example hundreds!), listing them (like above) 
will become annoying, buggy and time-consuming.
+In such cases, you can give @option{-c_all}.
+Upon execution, @code{_all} will be replaced with a comma-separated list of 
all the input columns.
+This allows you to add new columns easily, without having to worry about the 
number of input columns that you want anyway.
+A lower-level but more customizable method is to use the @command{seq} 
(sequence) command with the @code{-s} (separator) option set to @code{','}).
+For example, if you have 216 columns and only want to return columns 1 and 2 
as well as all the columns between 12 to 58 (inclusive), you can use the 
command below:
+
+@example
+$ asttable table.fits -c1,2,$(seq -s',' 12 58)
+@end example
+
 We are now ready to make our final table.
 We want it to have the magnitudes in all three filters, as well as the three 
possible colors.
 Recall that by convention in astronomy colors are defined by subtracting the 
bluer magnitude from the redder magnitude.
@@ -17339,8 +17351,11 @@ $ echo "7h34m35.5498 31d53m14.352s" | asttable
 
 ## Convert RA and Dec in degrees to sexagesimal (same can be done in a
 ## large table given as argument).
-echo "113.64812416667 31.88732" \
-     | asttable -c'arith $1 degree-to-ra $2 degree-to-dec'
+$ echo "113.64812416667 31.88732" \
+       | asttable -c'arith $1 degree-to-ra $2 degree-to-dec'
+
+## Extract columns 1 and 2, as well as all those between 12 to 58:
+$ asttable table.fits -c1,2,$(seq -s',' 12 58)
 @end example
 
 Table's input dataset can be given either as a file or from Standard input 
(piped from another program, see @ref{Standard input}).
@@ -17419,6 +17434,19 @@ The order of the output columns will be the same order 
given to the option or in
 This option is not mandatory, if no specific columns are requested, all the 
input table columns are output.
 When this option is called multiple times, it is possible to output one column 
more than once.
 
+
+@cartouche
+@noindent
+@strong{Sequence of columns:} when dealing with a large number catalogs 
(hundreds for example!), it will be frustrating, annoying and buggy to insert 
the columns manually.
+If you want to read all the input columns, you can use the special 
@option{_all} value to @option{--column} option.
+A more generic solution (for example if you want every second one, or all the 
columns within a special range) is to use the @command{seq} command's features 
with an extra @option{-s','} (so a comma is used as the ``separator'').
+For example if you want columns 1, 2 and all columns between 12 to 58 
(inclusive), you can use the following command:
+
+@example
+$ asttable table.fits -c1,2,$(seq -s',' 12 58)
+@end example
+@end cartouche
+
 @item -w FITS
 @itemx --wcsfile=FITS
 FITS file that contains the WCS to be used in the @code{wcs-to-img} and 
@code{img-to-wcs} operators of @ref{Column arithmetic}.