Crosswalk Lake IDs with mwlaxeref
In mwlaxeref: Cross-References Lake Identifiers Between Different Data Sets

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

mwlaxeref is an R package for going back and forth between different lake and waterbody identifiers such as: NHDHR+, NHD, LAGOS, and local state waterbody identification.

library(mwlaxeref)

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Basic Usage

For the examples used in this vignette, we'll use the following data from Wisconsin

head(wis_lakes, n = 3)

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Crosswalk functions are intuitive and easy to understand. For example, to crosswalk these Wisconsin lake IDs to NHDHR+, use the code below. The from_colname must be specified so that the function knows which column in wis_lakes contains the local IDs (the "lake.id" column in this case).

nhdhr_ids <- local_to_nhdhr(wis_lakes, from_colname = "lake.id", states = "wi")
head(nhdhr_ids, n = 3)

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Similarly, NHDHR+ IDs can be converted to LAGOS.

nhdhr_ids <- nhdhr_ids[, "nhdhr.id"]
lagos_ids <- nhdhr_to_lagos(nhdhr_ids)
head(lagos_ids, n = 3)

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Lake Identifiers

There are 6 different lake identification fields, and back and forth cross-walking functions exist for each of them. The six different ID fields are the first six column names of the lake_id_xref data.frame.

head(lake_id_xref, n = 3)

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State Shortcuts

Each state has its own shortcut function to each of the various other lake identifiers. For example, to go from Wisconsin local ID to LAGOS ID, you can use the following

lagos_id <- wi_to_lagos(wis_lakes, from_colname = "lake.id")
head(lagos_id, n = 3)

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Certain State Caveats

In some cases states contain multiple unique identifiers. In other cases there are multiple state agencies that each have their own unique ID. These duplicate instances often have the same NHDHR+, LAGOS, or other ID, so the agency and id_field arguments have been implemented to allow you to specify which agencies' unique ID to use (or which unique identification field if multiple exist within the same agency).

For example, in Michigan many lakes have both a UNIQUE ID and a NEW KEY field. Trying to go from NHDHR+ or LAGOS for these will yield duplicate results due to their being two IDs.

mi_nhdhr <- data.frame(nhdhr.id = "123397651")
nhdhr_to_mi(mi_nhdhr)

This duplication can be overcome by specifying the id_field argument as follows:

nhdhr_to_mi(mi_nhdhr, id_field = "NEW_KEY")

Different ID fields for certain states can be found in lake_id_xref under the column called id_field. For the example of Michigan, see unique(lake_id_xref$id.field[lake_id_xref$state == "mi"]).