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Relative difference of river length between 1800 and today

Source: R/getAxisPDiff.R
getAxisPDiff.Rd

Determine the relative difference in length of the River Elbe comparing the historical river axis from the year 1800 sf.axis1800 and the recent course of the river sf.axis for a specific hectometer and within an adjustable buffer distance. The returned value of the function is to be interpreted as in the following examples:

  • -3 ==> The historical axis was 3% longer than the recent axis with the selected polygons of sf.afe_csa.

  • 3 ==> The historical axis was 3% shorter than the recent axis with the selected polygons of sf.afe_csa.

Usage 

getAxisPDiff(x, b, bu = b)

Arguments

x

must be a single integer indexing one hectometer polygon of sf.afe_csa along the River Elbe. x must be element of seq(from = 1, to = length(sf.afe_csa), by = 1).

b

must be a single numeric specifying a buffersize to be included for the axis length computations around the indexed hectometer in m.

bu

is an optional single numeric specifying a separate upstream buffersize to be included for the axis length computations around the indexed hectometer in m (default = b).

Value

numeric with the proportion of change between River Elbe axis length in 1800 and today.

See also

sf.afe_csa, sf.axis, sf.axis1800

Examples 

   getAxisPDiff(3325, 200)
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> [1] 0.3427213
   getAxisPDiff(3900, 200)
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> Warning: attribute variables are assumed to be spatially constant throughout all geometries
#> [1] 0.9999389