This is the working routine behind the `concordance`

function. It
is not meant to be called by users, but is available for other packages
to use. Input arguments, for instance, are assumed to all be the
correct length and type, and missing values are not allowed: the calling
routine is responsible for these things.

```
concordancefit(y, x, strata, weights, ymin = NULL, ymax = NULL,
timewt = c("n", "S", "S/G", "n/G2", "I"), cluster, influence =0,
ranks = FALSE, reverse = FALSE, timefix = TRUE, keepstrata=10,
std.err = TRUE)
```

a list containing the results

- y
the response. It can be numeric, factor, or a Surv object

- x
the predictor, a numeric vector

- strata
optional numeric vector that stratifies the data

- weights
options vector of case weights

- ymin, ymax
restrict the comparison to response values in this range

- timewt
the time weighting to be used

- cluster, influence,ranks, reverse, timefix
see the help for the

`concordance`

function- keepstrata
either TRUE, FALSE, or an integer value. Computations are always done within stratum, then added. If the total number of strata greater than

`keepstrata`

, or`keepstrata=FALSE`

, those subtotals are not kept in the output.- std.err
compute the standard error; not doing so saves some compute time.

Terry Therneau

This function is provided for those who want a ``direct'' call to the concordance calculations, without using the formula interface. A primary use has been other packages. The routine does minimal checking of its input arguments, under the assumption that this has already been taken care of by the calling routine.

`concordance`