Review

my_func <- function(x,y,z){
  
  if(length(x)!=length(y) | length(x)!=length(z)){
  stop("All vectors must have same length")
}
  z <- factor(z)
  df <- data.frame(x,y,z)
  print(table(df$z))
   print(cor(x,y))
   boxplot(df$x)
   boxplot(df$y)
   write.csv(df, "df.csv")
}

my_func <- function(x,y,z){
if( length(x)!= length(y) | length(x)!= length(z)  ){
  stop("must be of the same length")
}
  
  x<-as.numeric(x)
  y <- as.numeric(y)
  # convert categorical variable
  z <- factor(z)
  tab <- table(z)

  # create dataframe
  df <- data.frame(x,y,z)

  # frequency table
  print(table(tab))

  # correlation
  print(cor(x,y,use="complete.obs"))

  # boxplots
  boxplot(df$x, main="Boxplot of x")
  boxplot(df$y, main="Boxplot of y")
  barplot(tab)
  # save file
  write.csv(df, "df.csv", row.names = FALSE)

  return(df)
}

x <- c(12,15,18,21,17,19,23,25,20,16)
y <- c(5,7,6,8,5,9,10,11,7,6)
z <- c("A","B","A","C","B","A","C","B","A","C")

my_func(x,y,z)

## tab
## 3 4 
## 2 1 
## [1] 0.8574632

##     x  y z
## 1  12  5 A
## 2  15  7 B
## 3  18  6 A
## 4  21  8 C
## 5  17  5 B
## 6  19  9 A
## 7  23 10 C
## 8  25 11 B
## 9  20  7 A
## 10 16  6 C