Provided by: stilts_3.1.2-2_all bug

NAME

       stilts-tskymap - Calculates sky density maps

SYNOPSIS

       stilts tskymap [ifmt=<in-format>] [istream=true|false] [in=<table>] [icmd=<cmds>]
                      [ocmd=<cmds>]
                      [omode=out|meta|stats|count|cgi|discard|topcat|samp|tosql|gui] [out=<out-
                      table>] [ofmt=<out-format>] [lon=<expr/deg>] [lat=<expr/deg>]
                      [tiling=hpx<K>|healpixnest<K>|healpixring<K>|htm<K>] [count=true|false]
                      [cols=<expr> ...] [combine=sum|mean|median|min|max|stdev|count|hit]
                      [complete=true|false]

DESCRIPTION

       tskymap  calculates a weighted density map (or, to put it another way, a histogram) on the
       sky from columns of an input table. The sky is divided up into some discrete set of  tiles
       according to a specified tessellation scheme (currently HEALPix or HTM are supported), and
       the required quantities are aggregated into bins corresponding to these tiles. The  output
       table  has a column giving the pixel index identifying each tile, plus one or more columns
       each representing an aggregation of a quantity from the input table.

       By default the number of rows from the input table falling within each tile is included as
       the  first  column  in the output table. But by specifying the cols and combine parameters
       you can add more columns giving the sum, mean, median or other statistics of  input  table
       columns or expressions as well.

       The  output  table  can then, for instance, be plotted using plot2sky's healpix layer type
       (though an alternative is to do that plot directly using a skydensity layer).

OPTIONS

       ifmt=<in-format>
              Specifies the format of the input table as specified by  parameter  in.  The  known
              formats  are  listed in SUN/256. This flag can be used if you know what format your
              table is in. If it has the special value (auto) (the default), then an attempt will
              be made to detect the format of the table automatically. This cannot always be done
              correctly however, in which case the program will exit  with  an  error  explaining
              which formats were attempted.

       istream=true|false
              If  set  true,  the  input  table  specified  by the in parameter will be read as a
              stream. It is necessary to give the ifmt parameter in this case. Depending  on  the
              required operations and processing mode, this may cause the read to fail (sometimes
              it is necessary to read the table more than once). It is not normally necessary  to
              set this flag; in most cases the data will be streamed automatically if that is the
              best thing to do. However it can sometimes  result  in  less  resource  usage  when
              processing large files in certain formats (such as VOTable).

       in=<table>
              The location of the input table. This may take one of the following forms:

                * A filename.

                * A URL.

                * The  special  value  "-", meaning standard input. In this case the input format
                  must be given explicitly using the ifmt parameter. Note that  not  all  formats
                  can be streamed in this way.

                * A  system  command  line  with  either  a  "<" character at the start, or a "|"
                  character at the end ("<syscmd" or "syscmd|"). This executes the given pipeline
                  and  reads  from its standard output. This will probably only work on unix-like
                  systems.
               In any case, compressed data in one of the supported  compression  formats  (gzip,
              Unix compress or bzip2) will be decompressed transparently.

       icmd=<cmds>
              Specifies  processing  to be performed on the input table as specified by parameter
              in, before any other processing has taken place. The value of this parameter is one
              or  more  of  the  filter commands described in SUN/256. If more than one is given,
              they must be separated  by  semicolon  characters  (";").  This  parameter  can  be
              repeated  multiple  times on the same command line to build up a list of processing
              steps. The sequence of commands given in this way defines the  processing  pipeline
              which is performed on the table.

              Commands may alteratively be supplied in an external file, by using the indirection
              character '@'. Thus a value of "@filename" causes the file filename to be read  for
              a  list of filter commands to execute. The commands in the file may be separated by
              newline characters and/or semicolons.

       ocmd=<cmds>
              Specifies processing  to  be  performed  on  the  output  table,  after  all  other
              processing  has  taken  place.  The  value  of this parameter is one or more of the
              filter commands described in SUN/256. If more than  one  is  given,  they  must  be
              separated  by  semicolon  characters (";"). This parameter can be repeated multiple
              times on the same command line to build up a list of processing steps. The sequence
              of commands given in this way defines the processing pipeline which is performed on
              the table.

              Commands may alteratively be supplied in an external file, by using the indirection
              character  '@'. Thus a value of "@filename" causes the file filename to be read for
              a list of filter commands to execute. The commands in the file may be separated  by
              newline characters and/or semicolons.

       omode=out|meta|stats|count|cgi|discard|topcat|samp|tosql|gui
              The  mode  in which the result table will be output. The default mode is out, which
              means that the result will be written as a new  table  to  disk  or  elsewhere,  as
              determined  by the out and ofmt parameters. However, there are other possibilities,
              which correspond to uses to which a table can be put other than outputting it, such
              as  displaying  metadata,  calculating  statistics, or populating a table in an SQL
              database. For some values of this parameter,  additional  parameters  (<mode-args>)
              are required to determine the exact behaviour.

              Possible values are

                * out

                * meta

                * stats

                * count

                * cgi

                * discard

                * topcat

                * samp

                * tosql

                * gui
               Use the help=omode flag or see SUN/256 for more information.

       out=<out-table>
              The  location of the output table. This is usually a filename to write to. If it is
              equal to the special value "-" (the default) the output table will  be  written  to
              standard output.

              This parameter must only be given if omode has its default value of "out".

       ofmt=<out-format>
              Specifies  the format in which the output table will be written (one of the ones in
              SUN/256 - matching is case-insensitive and you can use just the first few letters).
              If  it  has the special value "(auto)" (the default), then the output filename will
              be examined to try to guess what sort of file is required usually by looking at the
              extension. If it's not obvious from the filename what output format is intended, an
              error will result.

              This parameter must only be given if omode has its default value of "out".

       lon=<expr/deg>
              Longitude in degrees for the position of each row in  the  input  table.  This  may
              simply  be  a  column  name,  or  it may be an algebraic expression as explained in
              SUN/256. The sky system used here will determine the grid on which the  output  map
              is built.

       lat=<expr/deg>
              Latitude  in  degrees  for  the  position  of each row in the input table. This may
              simply be a column name, or it may be  an  algebraic  expression  as  explained  in
              SUN/256.  The  sky system used here will determine the grid on which the output map
              is built.

       tiling=hpx<K>|healpixnest<K>|healpixring<K>|htm<K>
              Describes the sky tiling scheme that is in use. One of the following values may  be
              used:

                * hpxK: alias for healpixnestK

                * healpixnestK: HEALPix using the Nest scheme at order K

                * healpixringK: HEALPix using the Ring scheme at order K

                * htmK: Hierarchical Triangular Mesh at level K
               So  for  instance hpx5 or healpixnest5 would both indicate the HEALPix NEST tiling
              scheme at order 5.

              At level K, there are 12*4^K HEALPix pixels, or 8*4^K HTM pixels on the  sky.  More
              information  about  these  tiling  schemes  can be found at the HEALPix and HTM web
              sites.

       count=true|false
              Controls whether a COUNT column is added to the output table along with  any  other
              columns  that may have been requested. If included, this reports the number of rows
              from the input table that fell within the corresponding bin.

       cols=<expr> ...
              Selects the columns to be aggregated into bins. The value is a space-separated list
              of  items,  where  each item may be either a column name or an expression using the
              expression language. The output table will have one column for each of the items in
              this list.

       combine=sum|mean|median|min|max|stdev|count|hit
              Combination mode for aggregating binned quantities. Possible values are:

                * sum: the sum of all the combined values

                * mean: the mean of the combined values

                * median: the median of the combined values (may be slow)

                * min: the minimum of all the combined values

                * max: the maximum of all the combined values

                * stdev: the sample standard deviation of the combined values

                * count: the number of non-blank values (weight is ignored)

                * hit: 1 if any values present, NaN otherwise (weight is ignored)

       complete=true|false
              Determines  whether  the output table contains a row for every pixel in the tiling,
              or only the rows for pixels in which some of the input data fell.

              The value of this parameter may affect performance as well as output. If  you  know
              that  most pixels on the sky will be covered, it's probably a good idea to set this
              true, and if you know that only a small patch of sky will be covered,  it's  better
              to set it false.

SEE ALSO

       stilts(1)

       If  the  package  stilts-doc  is installed, the full documentation SUN/256 is available in
       HTML format:
       file:///usr/share/doc/stilts-doc/sun256/index.html

VERSION

       STILTS version 3.1-2-debian

       This is the Debian version of Stilts, which lack the support  of  some  file  formats  and
       network protocols. For differences see
       file:///usr/share/doc/stilts/README.Debian

AUTHOR

       Mark Taylor (Bristol University)

                                             Mar 2017                           STILTS-TSKYMAP(1)