So I need to find the total number of issues by each author. Firstly I used this to separate the Author, Volume and its Issue. They are in this format
Edit: Was able to solve this. Appreciate the helps! Here's how I got it done.
meannation1 <- aggregate (Documents~Author, summation, length)
q7 <- merge(meannation,meannation1)
q7$Publication_Productivity <- ifelse(q7$Documents <= 1, '1', ifelse(q7$Documents <= 3, '2', '3'))
names(q7) <- c("Authors", "tf-Mean", "tfidf-Mean", "Total Number of Publications", "Publication Productivity")
I merged the data frame from my previous question that I created to find the mean, and then once the new data frame was created I just renamed the columns!