abconv: Derive linear conversion coefficients from a set of...

In MethComp: Analysis of Agreement in Method Comparison Studies

Description

If a method comparison model is defined as y_{mi} = α_m + β_m μ_i, m=1,2 y_mi = alpha_m + beta_m*mu_i, m=1,2 the coefficients of the linear conversion from method 1 to 2 are computed as: α_{2|1} = -α_2-α_1β_2/β_1 alpha_(2|1) = -alpha_2-alpha_1*beta_2/beta_1 beta_(2|1) = beta_2/beta_1 Morover the the point where the linear conversion function intersects the identity line is computed too.. The function is designed to work on numerical vectors of posterior samples from BUGS output.

Usage

abconv(
  a1,
  b1 = 1:4,
  a2 = NULL,
  b2 = NULL,
  col.names = c("alpha.2.1", "beta.2.1", "id.2.1")
)

Arguments

a1	Numerical vector of intercepts for first method. Alternatively a dataframe where the vectors are selected from.
b1	Numerical vector of slopes for first method. If a1 is a dataframe, b1 is assumed to be a numerical vector of length 4 pointing to the columns of a1 with the intercepts and slopes.
a2	Numerical vector of intercepts for second method.
b2	Numerical vector of slopes for second method.
col.names	Names for the resulting three vectors.

Value

A dataframe with three columns: intercept and slope for the conversion from method 1 to method 2, and the value where the conversion is the identity.

Author(s)

Bendix Carstensen, Steno Diabetes Center, http://BendixCarstensen.com

References

B Carstensen: Comparing and predicting between several methods of measurement, Biostatistics, 5, pp 399-413, 2004

See Also

BA.plot, MCmcmc

Examples

abconv( 0.3, 0.9, 0.8, 0.8 )

MethComp documentation built on Jan. 20, 2020, 1:12 a.m.