help Dxy and C-index calculation
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.MAZOUNI at igr.fr
<Chafika.MAZOUNI at 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