cohenk: Calculate Cohen's (1960, 1968) weighted kappa

In fpsim: Compute Measures of Foreign Policy Similarity/Agreement

Calculate Cohen's (1960, 1968) weighted kappa

Description

cohenk() takes two vectors and returns Cohen's kappa as an estimate of chance-corrected agreement.

Usage

cohenk(x1, x2, w_exp = 2, levels = NULL)

Arguments

x1	a vector, and one assumes an integer
x2	a vector, and one assumes an integer
w_exp	an exponent to apply to the weight matrix. Default is 2 for squared distances in the weight matrix. Supplying a 1 would make for linear distances.
levels	defaults to NULL, but an optional vector that defines the full sequence of values that could be observed in x1 and x2. If NULL, the function looks for observed values.

Details

The function subsets to complete cases of the two vectors for which you want Cohen's kappa.

The function implicitly assumes that x1 and x2 are columns in a data frame. One indirect check for this looks at whether x1 and x2 are the same length. The function will stop if they're not.

There will sometimes be instances, assuredly with alliances, where not all categories are observed. For example, the toy example I provide of Germany and Russia in 1914 includes no 2s. In the language of "ratings", the "rating" of 2 was available for Germany and Russia in 1914 but neither side used it. The levels argument allows you to specify the full sequence of values that could be observed, even if none were. It probably makes the most sense to always use this argument, even if the default behavior operates as if you won't.

Value

cohenk() takes two vectors and returns Cohen's kappa as an estimate of chance-corrected agreement.

References

Cohen, Jacob. 1960. "A Coefficient of Agreement for Nominal Scales." Educational and Psychological Measurement 20(1): 37-46.

Cohen, Jacob. 1968. "Weighted Kappa: Nominal Scale Agreement with Provision for Scaled Disagreement or Partial Credit." Psychological Bulletin 70(4): 213–220.

Examples

cohenk(gmyrus14$gmy, gmyrus14$rus, levels = 0:3) # with levels argument
cohenk(usamex46$vote1, usamex46$vote2) # levels argument not necessary here.

fpsim documentation built on July 5, 2026, 1:06 a.m.