Text Mining on extracted dataset

I want to implement some text mining operations repeatedly for a group of rows. Precisely, I have a dataset with class ids and feedback (textual data) and I need to perform text mining on all feedback data for each class id.

class_id; feedback

101; vast syllabus and lot of assignments
101; lot of material provided for the exam, overall tough
101; strict professor
103; easy grading
103; plenty of deadlines
103; limited study material

I'm utilizing this approach for text mining - https://www.r-bloggers.com/text-mining-and-word-cloud-fundamentals-in-r-5-simple-steps-you-should-know/ and have gotten so far. Please feel free to point out the flaws as I know it is far from working. In addition, any thoughts/suggestions and alternatives are welcome!

df <- read.csv("Wordall.csv")

#Creating sub-dataframes for Corpus

for (i in df$class_id)        
    comp[i] <- data.frame(df$class_id, df$feedback)  
    text <- readLines(comp[i])  
    docs <- Corpus(VectorSource(text))  

    #text mining operations...  
    i <- i+1