The inter-annual variability of a time series stored in an FLQuant object, is computed as \(|x_y - x_{y-1}) / x_{y-1}|\). The resulting object will be one year shorter than the input. The first year will be missing as values are assigned to the final year of each pair.
Examples
data(ple4)
# Compute inter-annual variability in catch
iav(catch(ple4))
#> An object of class "FLQuant"
#> , , unit = unique, season = all, area = unique
#>
#> year
#> age 1958 1959 1960 1961 1962 1963 1964
#> all 0.1330372 0.1847259 0.1215789 0.0132751 0.0564642 0.1150058 0.0477615
#> year
#> age 1965 1966 1967 1968 1969 1970 1971
#> all 0.0262144 0.0717180 0.0480213 0.0301291 0.0243120 0.0653893 0.0337214
#> year
#> age 1972 1973 1974 1975 1976 1977 1978
#> all 0.0578063 0.0142249 0.0427618 0.0468241 0.0634222 0.0570740 0.0743023
#> year
#> age 1979 1980 1981 1982 1983 1984 1985
#> all 0.0309460 0.0697257 0.0010639 0.0430649 0.1049299 0.0735235 0.0823874
#> year
#> age 1986 1987 1988 1989 1990 1991 1992
#> all 0.1301530 0.1047575 0.0219299 0.0736247 0.1418697 0.1293683 0.1168393
#> year
#> age 1993 1994 1995 1996 1997 1998 1999
#> all 0.0680792 0.1577328 0.1231082 0.0068560 0.1554476 0.1251388 0.0033755
#> year
#> age 2000 2001 2002 2003 2004 2005 2006
#> all 0.1445205 0.1225443 0.1225586 0.0710821 0.0907169 0.1821103 0.0234528
#> year
#> age 2007 2008 2009 2010 2011 2012 2013
#> all 0.0634175 0.0823385 0.0203357 0.0269798 0.0075226 0.1015176 0.0696424
#> year
#> age 2014 2015 2016 2017
#> all 0.0092539 0.0172577 0.0445777 0.0479687
#>
#> units: