Replace Design with rms (for general reasons not related to your question;
Design is about to be obsolete).
Negate Dxy. The linear predictor for the Cox model is relative log
hazard. Higher hazard means shorter survival time. For other survival
models the model is stated in terms of survival time.
Frank
On Fri, 19 Aug 2011 08:30:50 -0500, chafika.mazo...@igr.fr
<chafika.mazo...@igr.fr> wrote:
Dear professor,
I am currently using Design package and the cph formula for assessing
multivariable analysis.
I am tryng to get the C-index for my survival model based on Dxy
coefficient.
I am confused since there is a negative value.
Do I need to used the absolute Dxy ?
index.orig training test optimism index.corrected n
Dxy -0.341357727 -0.344002740 -0.341357727 -0.002645013
-0.338712715 40
R2 0.084694141 0.095440176 0.079077594 0.016362582
0.068331560 40
Slope 1.000000000 1.000000000 0.897999711 0.102000289
0.897999711 40
D 0.033368588 0.038458457 0.030983429 0.007475027
0.025893561 40
U -0.002890981 -0.002968495 0.003412045 -0.006380539
0.003489558 40
Q 0.036259569 0.041426951 0.027571385 0.013855566
0.022404003 40
Many thanks
Dr MAZOUNI
Institut Gustave Roussy
Department of breast surgical oncology
Villejuif, France
--
Frank E Harrell Jr Professor and Chairman School of Medicine
Department of Biostatistics Vanderbilt University
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