lambdas: Measurement error variances ratio
In BivRegBLS: Tolerance Interval and EIV Regression - Method Comparison Studies

Description Usage Arguments Details Value Author(s) References See Also Examples

Calculate the measurement error variances ratio of two devices (Y over X): λ and λ_{XY}

1	lambdas(data = NULL, xcol = NULL, ycol = NULL, conf.level = 0.95)

`data`	a data set (data frame or matrix).
`xcol`	a numeric vector to specify the X columns or a character vector with the column names.
`ycol`	a numeric vector to specify the Y columns or a character vector with the column names.
`conf.level`	a numeric value for the confidence level.

The data must be replicated to estimate the measurement error variances. If the number of replicates in X is equal to the number of replicates in Y, then λ and λ_{XY} are equal: λ is the ratio (Y over X) of the measurement error variances, while λ_{XY} is similar but takes also into account the number of replicates per device (nx and ny). Unbiased estimators (which is not the ratio of the two variances) for λ and λ_{XY} are also given.

A lambdas class object, a table with 2 rows (λ and λ_{XY}) and their confidence intervals and pvalues in columns (the null hypothesized value is 1).

Bernard G FRANCQ

Francq BG, Govaerts BB. How to regress and predict in a Bland-Altman plot? Review and contribution based on tolerance intervals and correlated-errors-in-variables models. Statistics in Medicine, 2016; 35:2328-2358.
Francq BG, Govaerts BB. Measurement methods comparison with errors-in-variables regressions. From horizontal to vertical OLS regression, review and new perspectives. Chemometrics and Intelligent Laboratory Systems, 2014; 134:123-139.

desc.stat

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library(BivRegBLS)
data(SBP)
lambdas(data=SBP,xcol=c("J1","J2","J3"),ycol=8:10)

Loading required package: ellipse

Attaching package: 'ellipse'

The following object is masked from 'package:graphics':

    pairs

$lambdas.Table
         Estimate Unbiased estimate Lower 95%CI Upper 95%CI       pvalue
Lambda    2.22256          2.196412     1.64379    3.005113 2.861344e-07
LambdaXY  2.22256          2.196412     1.64379    3.005113 2.861344e-07

attr(,"class")
[1] "lambdas"