RMST difference of 2 arms

## Usage

```
rmst(
data,
tau = 10,
var_label_tte = "tte",
var_label_event = "event",
var_label_group = "treatment",
formula = NULL,
reference = "control",
alpha = 0.05
)
```

## Arguments

- data
A time-to-event dataset with a column

`tte`

indicating the survival time and a column of`event`

indicating whether it is event or censor.- tau
RMST analysis time.

- var_label_tte
Column name of the TTE variable.

- var_label_event
Column name of the event variable.

- var_label_group
Column name of the grouping variable.

- formula
(default:

`NULL`

) A formula that indicates the TTE, event, and group variables using the syntax`Surv(tte, event) ~ group)`

(see Details below for more information). This is an alternative to specifying the variables as strings. If a formula is provided, the values passed to`var_label_tte`

,`var_label_event`

, and`var_label_group`

are ignored.- reference
A group label indicating the reference group.

- alpha
Type I error.

## Details

The argument `formula`

is provided as a convenience to easily specify the
TTE, event, and grouping variables using the syntax `Surv(tte, event) ~ group)`

. `Surv()`

is from the {survival} package (`survival::Surv()`

).
You can also explicitly
name the arguments passed to `Surv()`

, for example the following is
equivalent `Surv(event = event, time = tte) ~ group)`

. Note however that the
function `Surv()`

is never actually executed. Similarly, any other functions
applied in the formula are also ignored, thus you shouldn't apply any
transformation functions such as `log()`

since these will have no effect.

## Examples

```
data(ex1_delayed_effect)
rmst(
data = ex1_delayed_effect,
var_label_tte = "month",
var_label_event = "evntd",
var_label_group = "trt",
tau = 10,
reference = "0"
)
#> $method
#> [1] "RMST"
#>
#> $parameter
#> [1] 10
#>
#> $estimate
#> [1] 0.8650493
#>
#> $se
#> [1] 0.3900344
#>
#> $z
#> [1] 2.21788
#>
# Formula interface
rmst(
data = ex1_delayed_effect,
formula = Surv(month, evntd) ~ trt,
tau = 10,
reference = "0"
)
#> $method
#> [1] "RMST"
#>
#> $parameter
#> [1] 10
#>
#> $estimate
#> [1] 0.8650493
#>
#> $se
#> [1] 0.3900344
#>
#> $z
#> [1] 2.21788
#>
```