## Extract duplicates from a range

The following array formula in cell B11 extracts duplicates from cell range B3:E8, only one instance of each duplicate is returned.

Array formula in cell B11:

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### Explaining formula in cell B11

This formula consists of two parts, one extracts the row number and the other the column number needed to return the correct value.

INDEX(*reference*, *row*, *col*)

Step 1 to 6 shows how the row number is calculated, step 7 to 11 demonstrates how to calculate the column number.

#### Step 1 - Show one instance of each duplicate

The COUNTIF function counts values based on a condition or criteria, in this case, we take into account previously displayed values in order to prevent duplicates in our output list.

COUNTIF($B$10:B10, $B$3:$E$8)

becomes

COUNTIF("Duplicates", {"Apple", "Boysenberry", "Orange", "Papaya";"Coconut", "Crab apples", "Gooseberry", "Guava";"Honeyberry", "Jabuticaba", "Kiwano", "Kiwifruit";"Raspberry", "Plum", "Orange", "Papaya";"Peach", "Persimmon", "Plantain", "Plum";"Plumcot", "Raspberry", "Coconut", "Peach"})

and returns

{0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0}

#### Step 2 - Find duplicates

(COUNTIF($B$3:$E$8, $B$3:$E$8)<2)

becomes

({1,1,2,2;2,1,1,1;1,1,1,1;2,2,2,2;2,1,1,2;1,2,2,2}<2)

and returns

{TRUE,TRUE, FALSE,FALSE; FALSE,TRUE, TRUE,TRUE; TRUE,TRUE, TRUE,TRUE; FALSE,FALSE, FALSE,FALSE; FALSE,TRUE, TRUE,FALSE; TRUE,FALSE, FALSE,FALSE}

#### Step 3 - Add arrays

The parentheses makes sure that the arrays are added before comparing to 0 (zero).

(COUNTIF($B$10:B10, $B$3:$E$8)+(COUNTIF($B$3:$E$8, $B$3:$E$8)<2))=0

becomes

({0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0; 0,0,0,0}+{TRUE,TRUE, FALSE,FALSE; FALSE,TRUE, TRUE,TRUE; TRUE,TRUE, TRUE,TRUE; FALSE,FALSE, FALSE,FALSE; FALSE,TRUE, TRUE,FALSE; TRUE,FALSE, FALSE,FALSE})=0

becomes

{1,1,0,0;0,1,1,1;1,1,1,1;0,0,0,0;0,1,1,0;1,0,0,0}=0

and returns

{FALSE, FALSE, TRUE, TRUE;TRUE, FALSE, FALSE, FALSE;FALSE, FALSE, FALSE, FALSE;TRUE, TRUE, TRUE, TRUE;TRUE, FALSE, FALSE, TRUE;FALSE, TRUE, TRUE, TRUE}.

#### Step 4 - Replace TRUE with the corresponding row number

The IF function uses a logical expression to determine which value (argument) to return.

IF((COUNTIF($B$10:B10, $B$3:$E$8)+(COUNTIF($B$3:$E$8, $B$3:$E$8)<2))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)

becomes

IF({FALSE, FALSE, TRUE, TRUE;TRUE, FALSE, FALSE, FALSE;FALSE, FALSE, FALSE, FALSE;TRUE, TRUE, TRUE, TRUE;TRUE, FALSE, FALSE, TRUE;FALSE, TRUE, TRUE, TRUE}, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)

becomes

IF({FALSE, FALSE, TRUE, TRUE;TRUE, FALSE, FALSE, FALSE;FALSE, FALSE, FALSE, FALSE;TRUE, TRUE, TRUE, TRUE;TRUE, FALSE, FALSE, TRUE;FALSE, TRUE, TRUE, TRUE}, {1;2;3;4;5;6})

and returns

{FALSE,FALSE, 1,1; 2,FALSE,FALSE,FALSE; FALSE,FALSE,FALSE,FALSE; 4,4,4,4; 5,FALSE,FALSE,5; FALSE,6,6,6}

#### Step 5 - Find smallest value

The MIN function finds the minimum value in the array ignoring the boolean values.

MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+(COUNTIF($B$3:$E$8, $B$3:$E$8)<2))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1))

becomes

MIN({FALSE,FALSE, 1,1; 2,FALSE,FALSE,FALSE; FALSE,FALSE,FALSE,FALSE; 4,4,4,4; 5,FALSE,FALSE,5; FALSE,6,6,6})

and returns 1. This tells us that the first duplicate value is somewhere on row 1 in cell range B3:E8.

#### Step 6 - Return the row number of the first duplicate

This step is the same as step 1 to 5 and is repeated in order to get all values from the row.

MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1))

returns 1.

#### Step 7 - Extract values from row

INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1)

becomes

INDEX($B$3:$E$8, 1, , 1)

and returns

{"Apple","Boysenberry","Orange","Papaya"}.

#### Step 8 - Check if the values have been displayed in cells above

(COUNTIF($B$10:B10, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<>0)

becomes

(COUNTIF($B$10:B10, {"Apple","Boysenberry","Orange","Papaya"})<>0)

becomes

({0,0,0,0}<>0)

and returns

{FALSE,FALSE,FALSE,FALSE}.

#### Step 9 - Identify duplicates on the same row

(COUNTIF($B$3:$E$8, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<2)

becomes

(COUNTIF($B$3:$E$8, {"Apple","Boysenberry","Orange","Papaya"})<2)

becomes

({1,1,2,2}<2)

and returns

{TRUE,TRUE,FALSE,FALSE}.

This tells us that there are two duplicates on row 1.

#### Step 10 - Add arrays

(COUNTIF($B$10:B10, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<>0)+(COUNTIF($B$3:$E$8, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<2)

becomes

{FALSE,FALSE,FALSE,FALSE} + {TRUE,TRUE,FALSE,FALSE}

and returns

{1,1,0,0}

#### Step 11 - Identify duplicate and return relative column number

MATCH(0, IF(COUNTIF($B$10:B10, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))=0, 0, 1)+IF(COUNTIF($B$3:$E$8, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))>1, 0, 1), 0)

becomes

MATCH(0, {1,1,0,0}, 0)

and returns 3.

#### Step 12 - Return value

The INDEX function returns a value based on a row and column number.

=INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+(COUNTIF($B$3:$E$8, $B$3:$E$8)<2))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), MATCH(0, (COUNTIF($B$10:B10, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<>0)+(COUNTIF($B$3:$E$8, INDEX($B$3:$E$8, MIN(IF((COUNTIF($B$10:B10, $B$3:$E$8)+IF(COUNTIF($B$3:$E$8, $B$3:$E$8)>1, 0, 1))=0, ROW($B$3:$E$8)-MIN(ROW($B$3:$E$8))+1)), , 1))<2), 0))

becomes

=INDEX($B$3:$E$8, 1, 3)

and returns "Orange" in cell D3.

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