l1ccc {L1pack} | R Documentation |
L1 concordance correlation coefficient
Description
Calculates L1 concordance correlation coefficient for evaluating the degree of agreement between measurements generated by two different methods.
Usage
l1ccc(x, data, equal.means = FALSE, boots = TRUE, nsamples = 1000, subset, na.action)
Arguments
x |
a formula or a numeric matrix or an object that can be coerced to a numeric matrix. |
data |
an optional data frame (or similar: see |
equal.means |
logical, should the means of the measuring devices be considered equal? In which case the restricted estimation is carried out under this assumption. |
boots |
logical, hould use bootstrap to approximate the variances of the L1 estimators. |
nsamples |
number of bootstrap samples (default to 1000), only used if |
subset |
an optional expression indicating the subset of the rows of data that should be used in the fitting process. |
na.action |
a function that indicates what should happen when the data contain NAs. |
Value
A list with class 'l1ccc'
containing the following named components:
call |
a list containing an image of the |
x |
|
rho1 |
L1 estimate of the concordance correlation coefficient. |
var.rho1 |
approximate variance of the L1 concordance correlation coefficient,
only present if |
L1 |
list with L1 estimates using Laplace, and normal distributions, and U-statistics. |
Lin |
Lin's concordance correlation coefficient under the Laplace distribution. |
ustat |
L1 estimation of concordance coefficient using U-statistics,
a list containing the following elements |
center |
the estimated mean vector. |
Scatter |
the estimated Scatter (or Scale) matrix. |
logLik |
the log-likelihood at convergence. |
weights |
estimated weights corresponding to the Laplace distribution. |
Restricted |
available only if |
References
King, T.S., Chinchilli, V.M. (2001). A generalized concordance correlation coefficient for continuous and categorical data. Statistics in Medicine 20, 2131-2147.
King, T.S., Chinchilli, V.M. (2001). Robust estimators of the concordance correlation coefficient. Journal of Biopharmaceutical Statistics 11, 83-105.
Lin, L. (1989). A concordance correlation coefficient to evaluate reproducibility. Biometrics 45, 255-268.
Vallejos, R., Osorio, F., Ferrer, C. (2025+). A new coefficient to measure agreement between two continuous variables. Working paper.
Examples
## data from Bland and Altman (1986). The Lancet 327, 307-310.
x <- list(Large = c(494,395,516,434,476,557,413,442,650,433,
417,656,267,478,178,423,427),
Mini = c(512,430,520,428,500,600,364,380,658,445,
432,626,260,477,259,350,451))
x <- as.data.frame(x)
plot(Mini ~ Large, data = x, xlim = c(100,800), ylim = c(100,800),
xlab = "PERF by Large meter", ylab = "PERF by Mini meter")
abline(c(0,1), col = "gray", lwd = 2)
## estimating L1 concordance coefficient
z <- l1ccc(~ Mini + Large, data = x, boots = FALSE)
z
## output:
# Call:
# l1ccc(x = ~ Mini + Large, data = x, boots = FALSE)
#
# L1 coefficients using:
# Laplace Gaussian U-statistic
# 0.7456 0.7607 0.7642
#
# Lin's coefficients:
# estimate accuracy precision
# 0.9395 0.9974 0.9419