Overview
polimetrics is an R package that provides a collection of data and functions for common metrics used in political science research. The package focuses on two central concepts in the policy diffusion literature: geographical diffusion and ideological distance. It ships with curated datasets on U.S. state ideology and geographic structure, making it a self-contained toolkit for scholars studying how policies spread across states over time.
The methods implemented in polimetrics are derived from foundational work in the policy diffusion literature:
- Soule & King (2006) — American Journal of Sociology doi:10.1086/499908
- Berry et al. (1998) — American Journal of Political Science doi:10.2307/2991759
- Cruz-Aceves & Mallinson (2019) — State and Local Government Review doi:10.1177/0160323X20902818
- Grossback et al. (2004) — American Politics Research doi:10.1177/1532673X04263801
Installation
Install the released version from CRAN:
install.packages("polimetrics")Then load the package:
Functions
Policy Diffusion
These functions calculate the two primary metrics used in policy diffusion research. Both are flexible enough to accommodate any unit of analysis, time period, and policy adoption measure.
| Function | Description |
|---|---|
geog.diffuse() |
Calculates the proportion of geographically contiguous neighbors that have adopted a given policy in a given year — a measure of geographical diffusion |
ideo.dist() |
Calculates the ideological distance score between a state and prior policy adopters, based on the Grossback et al. (2004) method as clarified by Cruz-Aceves & Mallinson (2019) |
Examples
Geographical Diffusion
data <- Ideology_ERA
geog.diffuse(data, state, neighbors, year, era_status)This call appends a geographical diffusion score to the data frame, representing the proportion of each state’s neighboring states that had already adopted the ERA in each year.
Ideological Distance
data <- Ideology_ERA
ideo.dist(data, state, s_ideo, year, era_ratified)This call appends an ideological distance score to the data frame, capturing how ideologically distant each state was from prior ERA-adopting states in each year.
Included Datasets
polimetrics ships with a suite of datasets designed to work directly with its functions and support replication of common policy diffusion analyses.
| Dataset | Description |
|---|---|
Ideology |
Fording’s State Ideology Data — state- and citizen-level ideology scores for all U.S. states, 1960–2018 (3,050 observations, 4 variables). Source: rcfording.com |
Ideology_ERA |
Fording’s State Ideology Data adapted with Equal Rights Amendment ratification status — includes a binary variable for ERA ratification as used in Soule & King (2006) (300 observations, 5 variables) |
State_Neighbors |
US State Neighbor List — a character-string list of contiguous neighboring states for each of the 50 U.S. states (50 observations, 2 variables) |
US_States |
US States Information for Merging — common state names and abbreviations to facilitate merging with external datasets (50 observations, 5 variables) |
US_Counties |
US Counties Information for Merging — county-level names and identifiers for merging with external datasets |