The function outputs an averaged vector from a set of anchor terms' word
vectors. This average is roughly equivalent to the intersection of the
contexts in which each word is used. This semantic centroid can be used
for a variety of ends, and specifically as input to `CMDist()`

.
`get_centroid()`

requires a list of terms, string of terms, data.frame
or matrix. In the latter two cases, the first column will be used. The
vectors are aggregated using the simple average. Terms can be repeated,
and are therefore "weighted" by their counts.

`get_centroid(anchors, wv, missing = "stop")`

## Arguments

- anchors
List of terms to be averaged

- wv
Matrix of word embedding vectors (a.k.a embedding model)
with rows as words.

- missing
what action to take if terms are not in embeddings.
If action = "stop" (default), the function is stopped
and an error messages states which terms are missing.
If action = "remove", missing terms or rows with missing
terms are removed. Missing terms will be printed as a message.

## Value

returns a one row matrix

## Examples

```
# load example word embeddings
data(ft_wv_sample)
space1 <- c("spacecraft", "rocket", "moon")
cen1 <- get_centroid(anchors = space1, wv = ft_wv_sample)
space2 <- c("spacecraft rocket moon")
cen2 <- get_centroid(anchors = space2, wv = ft_wv_sample)
identical(cen1, cen2)
#> [1] TRUE
```