control$ID=rownames(control)

This line of code assigns the row names of the "control" data frame to a new variable called "control$ID".

The "$" operator is used to access a specific column or variable within a data frame. In this case, it is used to access the row names of the "control" data frame.

The "rownames()" function is used to retrieve the row names of a data frame. It returns a character vector containing the row names.

By assigning the row names to a new variable, we can use it for further analysis or manipulation of the data.