Rescale Aggregate id Measure to id Measure — rescale

Given an aggregate_id (e.g. reachcode in NHDPlus) measure and the from and to measure for an id (e.g. COMID flowline in NHDPlus), returns the measure along the id flowline. This is useful where many flowlines make up a single aggregate feature. "Measures" are typically referenced to the aggregate feature. Flowlines have a stated from-measure / to-measure. In some cases it is useful to rescale the measure such that it is relative only to the flowline.

from is downstream – 0 is the outlet to is upstream – 100 is the inlet

Usage

rescale_measures(measure, from, to)

Arguments

measure: numeric aggregate measure between 0 and 100
from: numeric from-measure relative to the aggregate
to: numeric to-measure relative to the aggregate

Value

numeric rescaled measure

Examples

rescale_measures(40, 0, 50)
#> [1] 80
rescale_measures(60, 50, 100)
#> [1] 20