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R Programming: Export/Output Data In R

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R Programming: Export/Output Data In R

  1. 1. r-squared Slide 1 www.r-squared.in/rprogramming R Programming Learn the fundamentals of data analysis with R.
  2. 2. r-squared Slide 2 Course Modules www.r-squared.in/rprogramming ✓ Introduction ✓ Elementary Programming ✓ Working With Data ✓ Selection Statements ✓ Loops ✓ Functions ✓ Debugging ✓ Unit Testing
  3. 3. r-squared Slide 3 Working With Data www.r-squared.in/rprogramming ✓ Data Types ✓ Data Structures ✓ Data Creation ✓ Data Info ✓ Data Subsetting ✓ Comparing R Objects ✓ Importing Data ✓ Exporting Data ✓ Data Transformation ✓ Numeric Functions ✓ String Functions ✓ Mathematical Functions
  4. 4. r-squared Slide 4 Exporting Data From R www.r-squared.in/rprogramming Objectives In this module, we will learn to: ● Output data to the console ● Output data to files ● Export data into text/CSV files ● Save R objects
  5. 5. r-squared Slide 5 Output Data To Console www.r-squared.in/rprogramming In this section, we will learn to output data to the console using the following functions: ✓ print ✓ cat ✓ paste ✓ paste0 ✓ sprintf
  6. 6. r-squared Slide 6 print() www.r-squared.in/rprogramming Description print() is a very basic function and as the name suggest it prints its arguments. Syntax print(x, ...) Returns Prints its arguments Documentation help(print)
  7. 7. r-squared Slide 7 print() www.r-squared.in/rprogramming Examples > # example 1 > x <- 3 > print(x) [1] 3 > x [1] 3 > # example 2 > name <- "Jovial" > lname <- "Mann" > print(name, lname) Error in print.default(name, lname) : invalid 'digits' argument > print(c(name, lname)) [1] "Jovial" "Mann"
  8. 8. r-squared Slide 8 cat() www.r-squared.in/rprogramming Description cat() concatenates its arguments and then outputs them. Syntax cat(... , file = "", sep = " ", fill = FALSE, labels = NULL, append = FALSE) Returns Concatenates and outputs its arguments Documentation help(cat)
  9. 9. r-squared Slide 9 cat() www.r-squared.in/rprogramming Examples > # example 1 # output to the console > name <- "Jovial" > age <- 28 > cat("Your name is", name, " and you are", age, " years old.") Your name is Jovial and you are 28 years old. > # example 2 # output to a file > name <- "Jovial" > age <- 28 > cat("Your name is", name, " and you are", age, " years old.", file = "words.txt")
  10. 10. r-squared Slide 10 cat() www.r-squared.in/rprogramming Examples > # example 3 # difference between print and cat > fname <- "Jovial" > lname <- "Mann" > print(c(fname, lname)) # throws an error [1] "Jovial" "Mann" > name <- c(fname, lname) > name [1] "Jovial" "Mann" > name <- "Jovial Mann" > print(name) [1] "Jovial Mann" > cat(fname, lname) Jovial Mann
  11. 11. r-squared Slide 11 paste() www.r-squared.in/rprogramming Description paste() converts its arguments to character strings and concatenates them. Syntax paste (..., sep = " ", collapse = NULL) Returns Character vector Documentation help(paste)
  12. 12. r-squared Slide 12 paste() www.r-squared.in/rprogramming Examples > # example 1 > x <- 1:10 > paste(x) [1] "1" "2" "3" "4" "5" "6" "7" "8" "9" "10" > paste(x, collapse = "") [1] "12345678910" > # example 2 > x <- LETTERS > x [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" [23] "W" "X" "Y" "Z" > paste(x) [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" [23] "W" "X" "Y" "Z" > paste(x, collapse = "") [1] "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  13. 13. r-squared Slide 13 paste() www.r-squared.in/rprogramming Examples > # example 3 > name <- "Jovial" > age <- 28 > paste(name, age) [1] "Jovial 28" > paste(name, age, sep = ",") [1] "Jovial,28" > paste(name, age, sep = "") [1] "Jovial28"
  14. 14. r-squared Slide 14 paste() www.r-squared.in/rprogramming Examples > # example 4 > alpha <- LETTERS[1:4] > numeric <- 1:4 > alpha_numeric <- paste(alpha, numeric) > alpha_numeric [1] "A 1" "B 2" "C 3" "D 4" > alpha_numeric <- paste(alpha, numeric, sep = "") > alpha_numeric [1] "A1" "B2" "C3" "D4"
  15. 15. r-squared Slide 15 paste0() www.r-squared.in/rprogramming Description paste0() does the same job as paste but with a blank separator. Syntax paste0(..., collapse = NULL) Returns Character vector of concatenated values. Documentation help(paste0)
  16. 16. r-squared Slide 16 paste0() www.r-squared.in/rprogramming Examples > # example 1 > alpha <- LETTERS[1:4] > numeric <- 1:4 > paste0(alpha, numeric) [1] "A1" "B2" "C3" "D4" > paste(alpha, numeric, sep = "") [1] "A1" "B2" "C3" "D4" > # example 2 > name <- "Jovial" > age <- 28 > paste0(name, age) [1] "Jovial28" > paste(name, age, sep = "") [1] "Jovial28"
  17. 17. r-squared Slide 17 sprintf() www.r-squared.in/rprogramming Description sprintf() returns a character vector containing text and objects. Syntax sprintf(fmt, ...) Returns Character vector Documentation help(sprintf)
  18. 18. r-squared Slide 18 sprintf() www.r-squared.in/rprogramming Examples > # example 1 > name <- "Jovial" > age <- 28 > sprintf("Your name is %s and you are %d years old", name, age) [1] "Your name is Jovial and you are 28 years old" # %s is replaced by the value in name and %d is replaced by value in age. s indicates string type and d indicates integer type.
  19. 19. r-squared Slide 19 Output Data To File www.r-squared.in/rprogramming In this section, we will learn to output data to a file using the following functions: ✓ writeLines ✓ write ✓ write.table ✓ write.csv ✓ sink ✓ dump
  20. 20. r-squared Slide 20 writeLines() www.r-squared.in/rprogramming Description writeLines() writes text lines to a connection or a file. Syntax writeLines(text, con = stdout(), sep = "n", useBytes = FALSE) Returns File with overwritten text. Documentation help(writeLines)
  21. 21. r-squared Slide 21 writeLines() www.r-squared.in/rprogramming Examples > # example 1 > details <- "My name is Jovial." > writeLines(details, "write.txt") > readLines("write.txt") [1] "My name is Jovial." > # example 2 > details_2 <- "I am 28 years old." > writeLines(details_2, "write.txt") > readLines("write.txt") [1] "I am 28 years old." # As you might have observed, writeLines overwrites the contents of a file. To append text to a file, we will use the write function.
  22. 22. r-squared Slide 22 write() www.r-squared.in/rprogramming Description write() writes/appends data to a file. Syntax write(x, file = "data", ncolumns = if(is.character(x)) 1 else 5, append = FALSE, sep = " ") Returns File with appended text. Documentation help(write)
  23. 23. r-squared Slide 23 write() www.r-squared.in/rprogramming Examples > # example 1 > name <- "My name is Jovial." > write(name, file = "write.txt") > readLines("write.txt") [1] "My name is Jovial." > age <- "I am 28 years old." > write(age, file = "write.txt", append = TRUE) > readLines("write.txt") [1] "My name is Jovial." "I am 28 years old."
  24. 24. r-squared Slide 24 write() www.r-squared.in/rprogramming Examples > # example 2 > x <- 1:5 > x [1] 1 2 3 4 5 > write(x, file = "write.txt", append = TRUE) > readLines("write.txt") [1] "My name is Jovial." "I am 28 years old." "1 2 3 4 5" > write(x, file = "write.txt", append = TRUE) > readLines("write.txt") [1] "My name is Jovial." "I am 28 years old." "1 2 3 4 5" "1 2 3 4 5" > write(x, file = "write.txt", append = TRUE, sep = "-") > readLines("write.txt") [1] "My name is Jovial." "I am 28 years old." "1 2 3 4 5" "1 2 3 4 5" [5] "1-2-3-4-5"
  25. 25. r-squared Slide 25 write.table() www.r-squared.in/rprogramming Description write.table() will convert the data into data.frame or matrix before writing it to a file. Syntax write.table(x, file = "", append = FALSE, quote = TRUE, sep = " ", eol = "n", na = "NA", dec = ".", row.names = TRUE, col.names = TRUE, qmethod = c("escape", "double"), fileEncoding = "") Returns File with data as a data frame or matrix. Documentation help(write.table)
  26. 26. r-squared Slide 26 write.table() www.r-squared.in/rprogramming Examples > # example 1 > m <- matrix(1:9, nrow = 3) > m [,1] [,2] [,3] [1,] 1 4 7 [2,] 2 5 8 [3,] 3 6 9 > # write to a text file > write.table(m, file = "table.txt") > readLines("table.txt") [1] ""V1" "V2" "V3"" ""1" 1 4 7" ""2" 2 5 8" [4] ""3" 3 6 9"
  27. 27. r-squared Slide 27 write.table() www.r-squared.in/rprogramming Examples > # example 2 > # write to a csv file > write.table(m, file = "table.csv") > readLines("table.csv") [1] ""V1" "V2" "V3"" ""1" 1 4 7" ""2" 2 5 8" [4] ""3" 3 6 9" > # example 3 > # append the transpose of the matrix > write.table(t(m), file = "table.txt", append = TRUE) > readLines("table.txt") [1] ""V1" "V2" "V3"" ""1" 1 4 7" ""2" 2 5 8" [4] ""3" 3 6 9" ""V1" "V2" "V3"" ""1" 1 2 3" [7] ""2" 4 5 6" ""3" 7 8 9"
  28. 28. r-squared Slide 28 write.table() www.r-squared.in/rprogramming > # example 4 > # use comma as a separator > write.table(t(m), file = "table.txt", append = TRUE, sep = ",") > readLines("table.txt") [1] ""V1" "V2" "V3"" ""1" 1 4 7" ""2" 2 5 8" [4] ""3" 3 6 9" ""V1" "V2" "V3"" ""1" 1 2 3" [7] ""2" 4 5 6" ""3" 7 8 9" ""V1","V2","V3"" [10] ""1",1,2,3" ""2",4,5,6" ""3",7,8,9" > # example 5 > # without row and column names > write.table(t(m), file = "table.txt", append = TRUE, row.names = FALSE, + col.names = FALSE) > readLines("table.txt") [1] ""V1" "V2" "V3"" ""1" 1 4 7" ""2" 2 5 8" [4] ""3" 3 6 9" ""V1" "V2" "V3"" ""1" 1 2 3" [7] ""2" 4 5 6" ""3" 7 8 9" ""V1","V2","V3"" [10] ""1",1,2,3" ""2",4,5,6" ""3",7,8,9" [13] "1 2 3" "4 5 6" "7 8 9"
  29. 29. r-squared Slide 29 write.csv() www.r-squared.in/rprogramming Description write.csv() will convert the data into data.frame or matrix before writing it to a CSV file. Syntax write.csv(data, file, row.names= FALSE) Returns CSV file Documentation help(write.csv)
  30. 30. r-squared Slide 30 write.csv() www.r-squared.in/rprogramming Examples > # example 1 > write.csv(mtcars, "mt.csv") > readLines("mt.csv") [1]""","mpg","cyl","disp","hp","drat","wt","qsec","vs","am","gear","carb"" [2] ""Mazda RX4",21,6,160,110,3.9,2.62,16.46,0,1,4,4" [3] ""Mazda RX4 Wag",21,6,160,110,3.9,2.875,17.02,0,1,4,4" [4] ""Datsun 710",22.8,4,108,93,3.85,2.32,18.61,1,1,4,1" > # example 2 > # without row names > write.csv(mtcars, "mt.csv", row.names = FALSE) > readLines("mt.csv") [1] ""mpg","cyl","disp","hp","drat","wt","qsec","vs","am","gear","carb"" [2] "21,6,160,110,3.9,2.62,16.46,0,1,4,4" [3] "21,6,160,110,3.9,2.875,17.02,0,1,4,4"
  31. 31. r-squared Slide 31 sink() www.r-squared.in/rprogramming Description sink() will divert the R output to a file/connection instead of the console. Syntax sink(file = NULL, append = FALSE, type = c("output", "message"), split = FALSE) Returns File with output Documentation help(sink)
  32. 32. r-squared Slide 32 sink() www.r-squared.in/rprogramming Examples > # example 1 > sink(file = "write.txt", append = TRUE, type = "output") > x <- 1:5 > x * 2 > readLines("write.txt") # nothing is printed on console > sink() # stop diverting output to file > readLines("write.txt") [1] "[1] 2 4 6 8 10" [2] "[1] "[1] 2 4 6 8 10"" [3] "[1] 2 4 6 8 10" [4] "[1] "[1] 2 4 6 8 10" "[1] "[1] 2 4 6 8 10""" [5] "[3] "[1] 2 4 6 8 10" "
  33. 33. r-squared Slide 33 sink() www.r-squared.in/rprogramming Examples > # example 2 > sink("example.txt") # start writing to example.txt file > x <- sample(1:10) > y <- sample(1:10) > cat("===============================n") > cat(" T-test between x and y n") > cat("===============================n") > t.test(x, y) > sink() # stop writing to the file > readLines("example.txt") [1] " [1] 2 5 4 6 9 3 10 1 7 8" [2] " [1] 6 10 5 1 4 2 9 7 3 8" [3] "===============================" [4] " T-test between x and y " [5] "===============================" [6] "" [7] "tWelch Two Sample t-test" [8] "" [9] "data: x and y" [10] "t = 0, df = 18, p-value = 1" [11] "alternative hypothesis: true difference in means is not equal to 0" [12] "95 percent confidence interval:" [13] " -2.844662 2.844662" [14] "sample estimates:" [15] "mean of x mean of y " [16] " 5.5 5.5 " [17] ""
  34. 34. r-squared Slide 34 dump() www.r-squared.in/rprogramming Description dump() takes a vector of names of R objects and produces text representation of objects on a file. Syntax dump(list, file = "dumpdata.R", append = FALSE, control = "all", envir = parent.frame(), evaluate = TRUE) Returns R file with text representation of R objects Documentation help(dump)
  35. 35. r-squared Slide 35 dump() www.r-squared.in/rprogramming Examples > # example 1 > x <- sample(1:10) > y <- sample(1:10) > xy <- list(x = x, y = y) # create a list > dump("xy", file = "dump.Rdmped") # write xy to dump.R file > unlink("dump.R") # close connection to dump.R file > rm("x", "y", "xy") # remove objects x, y and xy from the workspace > x # x is not available in the workspace Error: object 'x' not found > source("dump.Rdmped") # source dump.R file > xy $x [1] 6 4 9 10 2 8 5 3 7 1 $y [1] 8 7 6 9 3 1 5 2 4 10
  36. 36. r-squared Slide 36 save() www.r-squared.in/rprogramming Description save() writes an external representation of the R objects to specified file. Syntax save(R object, file_name) Returns/Creates R file with external representation of R objects Documentation help(save)
  37. 37. r-squared Slide 37 save() www.r-squared.in/rprogramming Examples > # example 1 > # save the following data in a R data file > x <- 1:10 > save(x, file = "x.RData") > # remove x from the workspace > rm(x) > # load x into workspace > load("x.RData") # we will look at this function in a file > # view the data > x [1] 1 2 3 4 5 6 7 8 9 10
  38. 38. r-squared Slide 38 Next Steps... www.r-squared.in/rprogramming In the next unit, we will learn to transform/reshape data in R: ● Reorder Data ● Subset/Filter Data ● Combine Data ● Transform Data
  39. 39. r-squared Slide 39 Connect With Us www.r-squared.in/rprogramming Visit r-squared for tutorials on: ● R Programming ● Business Analytics ● Data Visualization ● Web Applications ● Package Development ● Git & GitHub

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