## pairwise_rmst_test()


Pairwise RMST tests for all group pairs with multiple-comparison correction.


Usage

``` python
pairwise_rmst_test(
    surv,
    tau,
    group,
    *,
    estimand="difference",
    strata=None,
    correction="holm",
    conf_level=0.95,
    format=None
)
```


Compares RMST between all pairs of groups, with optional multiple-comparison adjustment. This answers the question: "Which pairs of groups have significantly different RMST?" when you have more than two groups.


## Parameters


`surv: Surv`  
A right-censored [Surv](Surv.md#greenwood.Surv) response (time-to-event data).

`tau: float`  
The restriction time for RMST calculation.

`group: Any`  
Group labels, one per observation. Can be array-like or categorical variable. Must have at least 2 unique levels to create pairs.

`estimand: str = ``"difference"`  
Type of estimand: `"difference"` (default), `"ratio"`, or `"percentage_difference"`.

`strata: Any | None = None`  
(Optional) Stratification variable. Each pairwise test is stratified by this factor.

`correction: str = ``"holm"`  
Multiple-comparison adjustment: `"holm"` (default), `"bh"`, `"bonferroni"`, or `"none"`.

`conf_level: float = ``0.95`  
Confidence level for intervals (the default is `0.95`).

`format: str | None = None`  
Output format: None (auto-detect), `"pandas"`, `"polars"`, or `"pyarrow"`.


## Returns


`DataFrame`  
One row per pair of groups with columns for group1, group2, RMST estimates, difference/ratio, confidence interval, test statistic, p-value, and adjusted p-value.


## Examples

Compare RMST across multiple groups with pairwise comparisons:


``` python
import greenwood as gw

lung = gw.load_dataset("lung", backend="polars")
y = gw.Surv.right(lung["time"], event=(lung["status"] == 2))
# If there are multiple groups, e.g., by stage:
# result = gw.pairwise_rmst_test(y, tau=365, group=lung["stage"])
```