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huynguyen96.dnu
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@huynguyen96dnu-22758
Last seen 4.6 years ago

Hi there, I have just constructed my own nomogram using *cph* function. Next, I compute C-index through D_xy value using the function *validate* of the package *rms* . It looks like:

# survival rate

```
mod.cox <- cph(formula = Surv(time, status) ~ age + weight,
data=train, x= TRUE, y= TRUE, surv = TRUE)
```

# Get the D_xy

```
v <- validate(mod.cox, dxy=TRUE, B=1000)
v
```

# Compute C-index

```
Dxy = v[rownames(v)=="Dxy", colnames(v)=="index.corrected"]
```

# The c-statistic according to the Dxy=2(c-0.5)

```
round(Dxy/2+0.5,3) #~0.5938927
```

So, I had C-index = 0.594. I wonder how can I get 95%CI from this?