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+# Exercise 09 
+
+setwd("~/Desktop/Fall-2021/Biocomputing/Biocomp_tutorial11")
+# Name of function and arguments
+
+# Takes a directory path and column number, default arguments are set for rows and override 
+exercise9 <- function(dir, column, rows=50, override=FALSE){
+# Reads data from each file in the specified directory
+  file_list <- list.files(path=dir) # This function assumes that all of the files in the directory are .csv files 
+  results<-NA # Creates results vector 
+  for(i in 1:length(file_list)){ 
+    data <- read.table(file_list[i])
+    if(nrow(data)<rows){ # Tests whether the number of rows in each file meets the specified row requirement
+      print(paste0("Error because number of rows in ", file_list[i], " does not meet the minimum requirement."))
+      if (override==TRUE){ # If override is true, then the coefficient of standard deviation will still be calculated 
+        print(paste0("Coefficient of variation for ", file_list[i], " will be added to results vector even though file did not meet row requirement."))
+        stdev <- sd(data[,column])
+        mean <- mean(data[,column])
+        results <- c(results, (stdev/mean))
+      }else{ # If override is false and rows do not meet the requirement, NA will be added to the results vector 
+        results <- c(results, NA) 
+        }
+    }else{
+      # If rows are greater than 50, add the coefficient of standard deviation to the results vector for each file 
+      stdev <- sd(data[,column])
+      mean <- mean(data[,column])
+      results <- c(results, (stdev/mean))
+    } 
+  }
+  return(results[-1])
+}
+
+# Call function 
+## Give path to directory for dir argument
+## Give number of column for column argument 
+## Optional to change default number of rows and override
+exercise9(dir,column)
+