I have a Google Form that fills up a new line with values in Sheet1!, column A and column B.

I am trying to create an =ARRAYFORMULA function in column C, which will populate the C cell in each new line created by the form with a random value, fetched from an array of cells in Sheet2!A1:A8.

The closest I got to doing it is with this array formula I placed in Sheet1!C1


It indeed enters a random value from Sheet2!A1:A8, however, the problem is that it changes all the previous values in column C to the same new random value it fetches for each new line created by the form.

What I need is that each new line created by the form will receive a different random value from the array.

Any ideas anyone?

  • 1
    Google scripts an option for you or must it be in vanilla functions? Commented May 19, 2018 at 3:00
  • Preferably I would have liked to do it with a sheet formula but a google script can be as efficient :-) Commented May 20, 2018 at 8:48

2 Answers 2


A script might be your best option because on each change, any random functions are reevaluated.

Go to Tools > Script editor and paste in the following script.

// Append a random value from an array when a form is submitted.
// The event parameter, e, contains the range data to append to the correct row.
function append(e) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();

  // get the form data coming in.
  var inputSheet = ss.getSheetByName('formData');

  // Get the array of random values from sheet 2.
  var randVals = ss.getSheetByName('Sheet2').getRange("A1:A8").getValues();

  // Get the range of the added row to the spreadsheet. Add one to the last column value so you're appending to col 3.
  var row = e.range.getRow()
  var col = e.range.getLastColumn()+1

  // Insert a random value from the values array to the correct row and column.
  inputSheet.getRange(row, col).setValue(randVals[Math.floor(Math.random() * randVals.length)]);


Once the script is in, go to Edit > Current project triggers and add a new trigger. Choose "from spreadsheet" and "on form submit" and the save.

Now, when your form is submitted, a random string from Sheet2 will be added to the last column of the spreadsheet.

  • Thank you @Brian. I tried the code but I get Error: TypeError: Cannot read property "range" from undefined. (line 13, file "Code") Commented May 24, 2018 at 12:53
  • You can't run it from the code editor because that range is defined when the form is submitted. Go to your form, make a test submission, and then look. Also, make sure your Sheet names match. You can change either the sheet or the script.
    – Brian
    Commented May 24, 2018 at 14:23

I had a situation to randomly pick M or F in a column. I used this formula in Google Sheets:

 =IF(RANDBETWEEN(1,2) = 1,"M","F")

Crude way, certainly not for long lists, but it works if your set of values is small.

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