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B.1.11 Strings

String manipulation and query functions.

concat( strings, ... )
Concatenates multiple values into a string. In some cases the same effect can be achieved by writing s1+s2+..., but this method makes sure that values are converted to strings, with the blank value invisible.
join( separator, words, ... )
Joins multiple values into a string, with a given separator between each pair.
equals( s1, s2 )
Determines whether two strings are equal. Note you should use this function instead of s1==s2, which can (for technical reasons) return false even if the strings are the same.
equalsIgnoreCase( s1, s2 )
Determines whether two strings are equal apart from possible upper/lower case distinctions.
startsWith( whole, start )
Determines whether a string starts with a certain substring.
endsWith( whole, end )
Determines whether a string ends with a certain substring.
contains( whole, sub )
Determines whether a string contains a given substring.
length( str )
Returns the length of a string in characters.
split( words )
Splits a string into an array of space-separated words. One or more spaces separates each word from the next. Leading and trailing spaces are ignored.

The result is an array of strings, and if you want to use the individual elements you need to use square-bracket indexing, with [0] representing the first object

split( words, regex )
Splits a string into an array of words separated by a given regular expression.

The result is an array of strings, and if you want to use the individual elements you need to use square-bracket indexing, with [0] representing the first object

matches( str, regex )
Tests whether a string matches a given regular expression.
matchGroup( str, regex )
Returns the first grouped expression matched in a string defined by a regular expression. A grouped expression is one enclosed in parentheses.
replaceFirst( str, regex, replacement )
Replaces the first occurrence of a regular expression in a string with a different substring value.
replaceAll( str, regex, replacement )
Replaces all occurrences of a regular expression in a string with a different substring value.
substring( str, startIndex )
Returns the last part of a given string. The substring begins with the character at the specified index and extends to the end of this string.
substring( str, startIndex, endIndex )
Returns a substring of a given string. The substring begins with the character at startIndex and continues to the character at index endIndex-1 Thus the length of the substring is endIndex-startIndex.
toUpperCase( str )
Returns an uppercased version of a string.
toLowerCase( str )
Returns an lowercased version of a string.
trim( str )
Trims whitespace from both ends of a string.
padWithZeros( value, ndigit )
Takes an integer argument and returns a string representing the same numeric value but padded with leading zeros to a specified length.
desigToRa( designation )
Attempts to determine the ICRS Right Ascension from an IAU-style designation such as "2MASS J04355524+1630331" following the specifications in the document http://cds.u-strasbg.fr/vizier/Dic/iau-spec.htx.

Note: this function should be used with considerable care. Such designators are intended for object identification and not for communicating sky positions, so that the resulting positions are likely to lack precision, and may be inaccurate. If positional information is available from other sources, it should almost certainly be used instead. But if there's no other choice, this may be used as a fallback.

Note also that a designator with no coordsystem-specific flag character (a leading "J", "B" or "G") is considered to be B1950, not J2000.

desigToDec( designation )
Attempts to determine the ICRS Declination from an IAU-style designation such as "2MASS J04355524+1630331" following the specifications in the document http://cds.u-strasbg.fr/vizier/Dic/iau-spec.htx.

Note: this function should be used with considerable care. Such designators are intended for object identification and not for communicating sky positions, so that the resulting positions are likely to lack precision, and may be inaccurate. If positional information is available from other sources, it should almost certainly be used instead. But if there's no other choice, this may be used as a fallback.

Note also that a designator with no coordsystem-specific flag character (a leading "J", "B" or "G") is considered to be B1950, not J2000.

desigToIcrs( designation )
Attempts to decode an IAU-style designation such as "2MASS J04355524+1630331" to determine its sky position, following the specifications in the document http://cds.u-strasbg.fr/vizier/Dic/iau-spec.htx.

Obviously, this only works where the sequence part of the designation takes one of the family of coordinate-based forms.

Note: this function should be used with considerable care. Such designators are intended for object identification and not for communicating sky positions, so that the resulting positions are likely to lack precision, and may be inaccurate. If positional information is available from other sources, it should almost certainly be used instead. But if there's no other choice, this may be used as a fallback.

Note also that a designator with no coordsystem-specific flag character (a leading "J", "B" or "G") is considered to be B1950, not J2000.


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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@jiscmail.ac.uk