| get_UM | R Documentation | 
Traverse NHDPlus network upstream main stem
get_UM(network, comid, distance = NULL, sort = FALSE, include = TRUE)
| network | data.frame NHDPlus flowlines including at a minimum: COMID,Pathlength, LevelPathI, and Hydroseq. | 
| comid | integer identifier to start navigating from. | 
| distance | numeric distance in km to limit how many COMIDs are | 
| sort | if TRUE, the returned COMID vector will be sorted in order of distance from the input COMID (nearest to farthest) | 
| include | if TRUE, the input COMID will be included in the returned COMID vector returned. The COMID that exceeds the distance specified is returned. | 
integer vector of all COMIDs upstream of the starting COMID along the mainstem
library(sf)
source(system.file("extdata", "sample_flines.R", package = "nhdplusTools"))
plot(sample_flines$geom)
start_COMID <- 11690196
UM_COMIDs <- get_UM(sample_flines, start_COMID)
plot(dplyr::filter(sample_flines, COMID %in% UM_COMIDs)$geom,
     col = "red", add = TRUE, lwd = 3)
UM_COMIDs <- get_UM(sample_flines, start_COMID, distance = 50)
plot(dplyr::filter(sample_flines, COMID %in% UM_COMIDs)$geom,
     col = "blue", add = TRUE, lwd = 2)
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