| DA.reg {MethComp} | R Documentation |
For each pair of methods in data, a regression of the differences on the
averages between methods is made and a linear relationship between methods
with prediction standard deviations is derived.
DA.reg(data)
data |
A Meth object. May also be a data frame with columns
meth, item and y. |
If the input object contains replicate measurements these are taken as separate items in the order they appear in the dataset.
A three-dimensional array, with dimensions From, To (both
with levels equal to the methods in data) and an unnamed dimension
with levels "alpha", "beta", "sd.pred",
"beta=1" and "s.d.=K". Conversting from method j to
method k using
y_{k|l}=α+β y_l
with prediction
standard deviation σ, just requires the entries
[l,k,c("alpha","beta","sd.pred"]. The two last entries ae p-values
for the hypothese the β=1 and that the standard error is
constant over the range.
Bendix Carstensen, Steno Daibetes Center, bxc$steno.dk
B Carstensen: Limits of agreement: How to use the regression of differences on averages. Technical Report 08.6, Department of Biostatistics, University of Copenhagen, http://www.pubhealth.ku.dk/bs/publikationer/Research_report_08-6.pdf, 2008.
data( milk ) DA.reg( milk ) round( ftable( DA.reg( milk ) ), 3 ) data( sbp ) round( ftable( DA.reg( sbp ) ), 3 )