FSTATISTIC (Apr2013) ftools.futils FSTATISTIC (Apr2013)
NAME
fstatistic -- Compute statistics (min, max, mean, etc..) for a
given column in a FITS ASCII or binary table file extension.
USAGE
fstatistic infile[ext#] colname
DESCRIPTION
This task computes the mean, standard deviation, minimum, and
maximum of the data in the specified column. The rows included in
the calculation can be specified. Maximum and minimum values can
be specified, outside of which the data will not be included in the
calculation. If either the maximum and/or the minimum requested is
equal to INDEF, it will not be tested for. The output is written
to STDOUT and to the parameter file by default. The output may
also be directed to a file.
Note that in the case of vector columns, statistics are computed on
the *sum* of the vector elements in each row of the table (i.e. the
reported mean value is that of all the individual sums in each
row). For alternate vector column handling, please use the ftstat
task which computes statistics for the total number of elements, in
all of the rows of each column.
PARAMETERS
infile [filename]
The name of the FITS file (including extension number in square
brackets) of the input FITS table.
colname [string]
Name of the column in the input table. The statistics are
calculated for this column. If the column is
multi-dimensional, the statistics are based on the sum of all
elements of the column. The statistics on a specific element
of the vector/array can be requested by specifying the element:
COLNAME(10,4) or COLNAME[30;4].
rows [string]
String containing the requested rows to include in the
calculation. If the value is "-", the entire file will be used.
(outfile=STDOUT) [filename]
Optional output file name to write the statistics. If
preceeded by a !, an existing file of the same name will be
overwritten.
(maxval=INDEF) [real]
The maximum value to include in the calculation. A value of
INDEF indicates that no upper limit will be used in the
calculation.
(minval=INDEF) [real]
The minimum value to include in the calculation. A value of
INDEF indicates no lower limit.
(sum= ) [real]
Value of the sum of the specified column is returned to this
parameter.
(mean= ) [real]
Value of the mean of the specified column is returned to this
parameter.
(sigma= ) [real]
The value of the standard deviation is written to this
parameter.
(min= ) [real]
The minimum value in the requested column is written into this
parameter.
(max= ) [real]
The maximum value in the requested column is written to this
parameter.
(numb= ) [integer]
The number of values actually used in the calculation is
returned.
(clobber=no) [boolean]
If true, an existing file of the same name as the requested
output file will be overwritten.
EXAMPLES
1. Compute the statistics for the 'FLUX' column in the second
extension in the input FITS file named 'myfile.fits':
ft> fstatistic myfile.fits[2] flux
SEE ALSO
ftstat, ftlist