Intraclass Correlation in Python Module?

Question

I'm looking to calculate intraclass correlation (ICC) in Python. I haven't been able to find an existing module that has this feature. Is there an alternate name, or should I do it myself? I'm aware this question was asked a year ago on Cross Validated by another user, but there were no replies. I am looking to compare the continuous scores between two raters.

Answer 1

There are several implementations of the ICC in R. These can be used from Python via the rpy2 package. Example:

from rpy2.robjects import DataFrame, FloatVector, IntVector
from rpy2.robjects.packages import importr
from math import isclose

groups = [1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4,
          4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8, 8]
values = [1, 2, 0, 1, 1, 3, 3, 2, 3, 8, 1, 4, 6, 4, 3,
          3, 6, 5, 5, 6, 7, 5, 6, 2, 8, 7, 7, 9, 9, 9, 9, 8]

r_icc = importr("ICC")
df = DataFrame({"groups": IntVector(groups),
                "values": FloatVector(values)})
icc_res = r_icc.ICCbare("groups", "values", data=df)
icc_val = icc_res[0] # icc_val now holds the icc value

# check whether icc value equals reference value
print(isclose(icc_val, 0.728, abs_tol=0.001))