combine multiple vectors into one

## Usage

`combn_vector(..., method = "first", invalid = NA)`

## Arguments

- ...
vectors

- method
how to combine, should be one of
`first|last`

, or one of `sum|mean|median`

for numeric vector,
or some characters (e.g. `,|.| |;`

) for character vector

- invalid
invalid value to ignore, `NA`

as default

## Examples

```
x1 <- c(1, 2, NA, NA)
x2 <- c(3, NA, 2, NA)
x3 <- c(4, NA, NA, 3)
combn_vector(x1, x2, x3, method = "sum")
#> [1] 8 2 2 3
```