simulate_grades_courses.R

# Ref: https://twitter.com/Amit_Levinson/status/1187754568014336002 

set.seed(2019)
gen_grades <- function(n, avg, sd, min, max, nsmpl) {
  smpl <- rnorm(nsmpl, avg, sd)
  smpl <- smpl[smpl >= min & smpl <= max]
  if (length(smpl) >= n) {
    return(sample(smpl, n))
  } else {
    stop(simpleError("Not enough sample data. Increase 'nsmpl'"))
  }
}

grdmat <- matrix(nrow = 100, ncol = 10)

for(i in 1:10) {
  grdmat[,i] = floor(gen_grades(n = 100, avg = 70, sd = 10, min = 54, max = 100, nsmpl = 1000))
}

df <- as.data.frame(grdmat)
rownames(df) <- paste0("Student_",1:100)
colnames(df) <- paste0("Course_",LETTERS[1:10])

> head(df)
          Course_A Course_B Course_C Course_D Course_E Course_F
Student_1       75       57       78       73       75       71
Student_2       99       57       61       71       63       75
Student_3       79       81       63       65       85       67
Student_4       57       73       56       79       76       96
Student_5       61       87       66       78       70       74
Student_6       66       75       91       67       78       69
          Course_G Course_H Course_I Course_J
Student_1       76       60       85       84
Student_2       72       55       79       78
Student_3       62       92       55       59
Student_4       73       72       73       75
Student_5       88       73       73       68
Student_6       64       68       82       71