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Functions which perform aggregating operations on array-valued cells.
The functions in this class such as mean
, sum
,
maximum
etc can only be used on values which are already arrays.
In most cases that means on values in table columns which are declared
as array-valued. FITS and VOTable tables can have columns which contain
array values, but other formats such as CSV cannot.
There is also a set of functions named array
with various
numbers of arguments, which let you assemble an array value from a list
of scalar numbers. This can be used for instance to get the mean of
a set of three magnitudes by using an expression like
"mean(array(jmag, hmag, kmag))
".
-
sum( array )
- Returns the sum of all the non-blank elements in the array.
If
array
is not a numeric array, null
is returned.
-
mean( array )
- Returns the mean of all the non-blank elements in the array.
If
array
is not a numeric array, null
is returned.
-
variance( array )
- Returns the population variance of all the non-blank elements
in the array. If
array
is not a numeric array,
null
is returned.
-
stdev( array )
- Returns the population standard deviation of all the non-blank elements
in the array. If
array
is not a numeric array,
null
is returned.
-
minimum( array )
- Returns the smallest of the non-blank elements in the array.
If
array
is not a numeric array, null
is returned.
-
maximum( array )
- Returns the largest of the non-blank elements in the array.
If
array
is not a numeric array, null
is returned.
-
median( array )
- Returns the median of the non-blank elements in the array.
If
array
is not a numeric array, null
is returned.
-
quantile( array, quant )
- Returns a quantile value of the non-blank elements in the array.
Which quantile is determined by the
quant
value;
values of 0, 0.5 and 1 give the minimum, median and maximum
respectively. A value of 0.99 would give the 99th percentile.
-
size( array )
- Returns the number of elements in the array.
If
array
is not an array, zero is returned.
-
count( array )
- Returns the number of non-blank elements in the array.
If
array
is not an array, zero is returned.
-
join( array, joiner )
- Returns a string composed of concatenating all the elements of an
array, separated by a joiner string.
If
array
is not an array, null is returned.
-
array( x1 )
- Returns a numeric array built from a given element.
-
array( x1, x2 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3, x4 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3, x4, x5 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3, x4, x5, x6 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3, x4, x5, x6, x7 )
- Returns a numeric array built from given elements.
-
array( x1, x2, x3, x4, x5, x6, x7, x8 )
- Returns a numeric array built from given elements.
Next Previous Up Contents
Next: Fluxes
Up: General Functions
Previous: Maths
TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page:
http://www.starlink.ac.uk/topcat/
Author email:
m.b.taylor@bristol.ac.uk
Mailing list:
topcat-user@bristol.ac.uk