I have a character vector containing 5 elements. 4 elements contain a single name, but one element contains two names, separated by a comma.

For example:

```
string <- c("Eric", "John", "Dora", "Michael, James", "Susan")

string
[1] "Eric"           "John"           "Dora"           "Michael, James" "Susan"

```

I want to separate the fourth element into two separate elements, such that:

```
string

[1] "Eric"    "John"    "Dora"    "Michael" "James"   "Susan" 

```

Surely, this should be very easy. Yet, I can't seem to figure it out.

When I use 

```
strsplit(string, ",")

```

The result is a list.

I believe there are ways to convert that list to a data.frame and then stack those columns, but I wonder if there is some regex magic or `substring` code for this issue?