How to extract attributes from cox.zph R function

Question

I need to extract the `p` attribute of a specific row in the output of `cox.zph` function in R. To put you in question, I describe my problem as follows, step by step with an example: ``` require('survival') # I create the simplest test data set test1 <- list(time=c(4,3,1,1,2,2,3), status=c(1,1,1,0,1,1,0), x=c(0,2,1,1,1,0,0), sex=c(0,0,0,0,1,1,1)) # Fit a stratified model coxmodel <- coxph(Surv(time, status) ~ x + strata(sex), test1) ``` And then, I use `cox.zph` function: ``` zph <- cox.zph(coxmodel) ``` With the following output: ``` rho chisq p x 0.354 0.322 0.57 ``` I tried to get `p` attribute value (in this case, 0.57) by using `attributes(zph)` but `p` doesn't appear in order to do something like `zph$p`. I also used `plyr` package with no results. Does anyone could help me? Thanks.

Accepted Answer

Here it is:

```
zph$table[ , "p" ]
```

The you can access the members of the zph object using `$`, since it is a list:

```
names( zph )
# returns:
# [1] "table"     "x"         "y"         "var"       "call"      "transform"
```

Then look up `zph$table` and presto.

In R, usually the different "slots" of an object are accessible through `$` (S3 OO framework) or `@` (S4 OO framework).

How to extract attributes from cox.zph R function

Solution

Problem