R help - Dec 2008 - concordance correlation coefficient using R

Hi.
I have data which i would want to assess the degree of  agreement
between two assays, e.g., to evaluate reproducibility or for
inter-rater reliability. I have used the  Pearson product-moment
correlation coefficient. It looks good ranginging between 0.90 to
0.998. Though this looks good. I am told the Concordance correlation
coefficient will give a better picture of how reproducible the assay
is.
Does any one know how to run such a test using R? If so can you kindly
provide the code, and bit of explanations to spruce it up?

Thank you

Paul

You can look at the fonction icc in the package psy.
Best regards,
Bruno




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Bruno Falissard
INSERM U669, PSIGIAM
"Paris Sud Innovation Group in Adolescent Mental Health"
Maison de Solenn
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75679?Paris cedex 14, France
tel : (+33) 6 81 82 70 76
fax : (+33) 1 58 41 28 43
web?site : http://perso.wanadoo.fr/bruno.falissard/
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-----Message d'origine-----
De?: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] De
la part de paul murima
Envoy??: dimanche 7 d?cembre 2008 16:23
??: r-help at r-project.org; r-help at stat.math.ethz.ch
Objet?: [R] concordance correlation coefficient using R


Hi.
I have data which i would want to assess the degree of  agreement
between two assays, e.g., to evaluate reproducibility or for
inter-rater reliability. I have used the  Pearson product-moment
correlation coefficient. It looks good ranginging between 0.90 to
0.998. Though this looks good. I am told the Concordance correlation
coefficient will give a better picture of how reproducible the assay
is.
Does any one know how to run such a test using R? If so can you kindly
provide the code, and bit of explanations to spruce it up?

Thank you

Paul

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on 12/07/2008 09:23 AM paul murima wrote:
> Hi.
> I have data which i would want to assess the degree of  agreement
> between two assays, e.g., to evaluate reproducibility or for
> inter-rater reliability. I have used the  Pearson product-moment
> correlation coefficient. It looks good ranginging between 0.90 to
> 0.998. Though this looks good. I am told the Concordance correlation
> coefficient will give a better picture of how reproducible the assay
> is.
> Does any one know how to run such a test using R? If so can you kindly
> provide the code, and bit of explanations to spruce it up?
> 
> Thank you
> 
> Paul
Look at the epi.ccc function in the epiR CRAN package. More information
here:

 http://bm2.genes.nig.ac.jp/RGM2/R_current/library/epiR/man/epi.ccc.html

You might also want to review Martin Bland's page pertaining to the
design and analysis of measurement agreement studies:

 http://www-users.york.ac.uk/~mb55/meas/meas.htm


HTH,

Marc Schwartz