How to use the COMBIN function
The COMBIN function returns the number of combinations for a specific number of elements out of a larger number of elements.
Table of Contents
1. COMBIN Function Syntax
COMBIN(number, number_chosen)
2. COMBIN Function Arguments
number | Required. A whole number larger than 0 (zero) represents the total number of elements. |
number_chosen | Required. A whole number larger than 0 (zero) represents the number of elements in each combination. |
I recommend you press with left mouse button on the following link if you want to read about the difference between combinations and permutations in greater detail.
3. COMBIN Function Example
Formula in cell F3:
Column B, C and D demonstrate how many combinations there are when 2 elements are selected out of 3 elements [A, B, C].
The three combinations are [A,B] ,[A,C] and [B,C]. The elements' internal order is not important, that is why [A,B] and [B,A] is the same combination.
4. COMBIN Function alternative
Here is how the COMBIN function calculates in greater detail, see the image above. The formula below is the same as the formula shown in the image above, FACT function is the ! (factorial character).
C = Combinations
n = objects (number)
r = sample (number_chosen)
Formula in cell C7:
3.1 Explaining formula
Step 1 - Calculate the numerator
The FACT function calculates the factorial of a number.
FACT(number)
FACT(C5)
becomes
FACT(3)
and returns 6. 3*2*1 equals 6.
Step 2 - Calculate the denominator
(FACT(C6)*FACT(C5-C6))
C5-C6
becomes
3-2 and returns 1.
FACT(1) is 1.
FACT(2) is 2. 2*1 equals 2.
The parentheses let you control the order of operation.
(FACT(C6)*FACT(C5-C6))
becomes
2*1 equals 2.
Step 3 - Calculate the division
FACT(C5)/(FACT(C6)*FACT(C5-C6))
becomes
6/2 equals 3.
5. List combinations - Excel 365 formula
This section demonstrates how to list combinations based on n (numbers) and r (numbers_chosen). Check out this article: Return all combinations that describes a User Defined Function that lists combinations. That UDF should work for most Excel versions.
Excel 365 dynamic array formula in cell I2:
4.1 Explaining formula
Step 1 - To the power of
This step calculates the number of rows needed to calculate every combination.
2^F2
becomes
2^6 equals 64.
Step 2 - Create an array from 0 (zero) to n
The SEQUENCE function creates a sequence of numbers.
SEQUENCE(rows, [columns], [start], [step])
SEQUENCE(2^F2)-1
becomes
SEQUENCE(64)-1
becomes
{1; 2; 3; ... ; 64} - 1
and returns
{0; 1; 2; 3; ... ; 63}.
Step 3 - Divide vertical array by horizontal array
(SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)
becomes
{0; 1; 2; 3; ... ; 63}/2^SEQUENCE(,F2,0)
becomes
{0; 1; 2; 3; ... ; 63}/2^{0,1,2,3,4,5}
becomes
{0; 1; 2; 3; ... ; 63}/{1,2,4,8,16,32}
and returns
{0, 0, 0, 0, 0, 0;1, ... , 1.96875}.
Step 3 - Remove decimals
The INT function removes the decimal part from positive numbers and returns the whole number (integer) except negative values are rounded down to the nearest integer.
INT(number)
INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0))
becomes
INT({0, 0, 0, 0, 0, 0;1, ... , 1.96875})
and returns
{0, 0, 0, 0, 0, 0; 1, ... , 1}
Step 4 - Calculate the remainder
The MOD function returns the remainder after a number is divided by a divisor.
MOD(number, divisor)
MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2)
becomes
MOD({0, 0, 0, 0, 0, 0; 1, ... , 1}, 2)
and returns
{0, 0, 0, 0, 0, 0; 1, ... , 1}.
Step 5 - Calculate the matrix product of two arrays
The MMULT function calculates the matrix product of two arrays, an array as the same number of rows as array1 and columns as array2.
MMULT(array1, array2)
MMULT(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(, F2,0)), 2), SEQUENCE(F2)^0)
becomes
MMULT({0, 0, 0, 0, 0, 0; 1, ... , 1}, {1; 1; 1; 1; 1; 1})
and returns
{0; 1; 1; 2; 1;Â ... ; 6}
Step 6 - Check if number is equal to numbers_chosen
The equal sign lets you compare value to value in an Excel formula, the result is a boolean value TRUE or FALSE.
MMULT(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),SEQUENCE(F2)^0)=F3
becomes
{0; 1; 1; 2; 1;Â ... ; 6}=4
and returns
{FALSE; FALSE; FALSE; FALSE;Â ... ; FALSE}
Step 7 - Filter combinations based on the number chosen
The FILTER function lets you extract values/rows based on a condition or criteria.
FILTER(array, include, [if_empty])
FILTER(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),MMULT(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),SEQUENCE(F2)^0)=F3)
becomes
FILTER(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),{FALSE; FALSE; FALSE; FALSE;Â ... ; FALSE})
becomes
FILTER({0, 0, 0, 0, 0, 0; 1, ... , 1},{FALSE; FALSE; FALSE; FALSE;Â ... ; FALSE})
and returns
{1, 1, 1, 1, 0, 0;
1, 1, 1, 0, 1, 0;
1, 1, 0, 1, 1, 0;
1, 0, 1, 1, 1, 0;
0, 1, 1, 1, 1, 0;
1, 1, 1, 0, 0, 1;
1, 1, 0, 1, 0, 1;
1, 0, 1, 1, 0, 1;
0, 1, 1, 1, 0, 1;
1, 1, 0, 0, 1, 1;
1, 0, 1, 0, 1, 1;
0, 1, 1, 0, 1, 1;
1, 0, 0, 1, 1, 1;
0, 1, 0, 1, 1, 1;
0, 0, 1, 1, 1, 1}
Step 8 - Populate the array
The IF function returns one value if the logical test is TRUE and another value if the logical test is FALSE.
IF(logical_test, [value_if_true], [value_if_false])
IF(FILTER(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),MMULT(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),SEQUENCE(F2)^0)=F3),TRANSPOSE(C2:C7),"")
becomes
IF({1, 1, 1, 1, 0, 0;
1, 1, 1, 0, 1, 0;
1, 1, 0, 1, 1, 0;
1, 0, 1, 1, 1, 0;
0, 1, 1, 1, 1, 0;
1, 1, 1, 0, 0, 1;
1, 1, 0, 1, 0, 1;
1, 0, 1, 1, 0, 1;
0, 1, 1, 1, 0, 1;
1, 1, 0, 0, 1, 1;
1, 0, 1, 0, 1, 1;
0, 1, 1, 0, 1, 1;
1, 0, 0, 1, 1, 1;
0, 1, 0, 1, 1, 1;
0, 0, 1, 1, 1, 1},TRANSPOSE(C2:C7),"")
The TRANSPOSE function allows you to convert a vertical range to a horizontal range, or vice versa.
TRANSPOSE(array)
TRANSPOSE(C2:C7)
becomes
TRANSPOSE({"A"; "B"; "C"; "D"; "E"; "F"})
and returns
{"A", "B", "C", "D", "E", "F"}.
IF({1, 1, 1, 1, 0, 0;
...
0, 0, 1, 1, 1, 1},TRANSPOSE(C2:C7),"")
becomes
IF({1, 1, 1, 1, 0, 0;
...
0, 0, 1, 1, 1, 1},{"A", "B", "C", "D", "E", "F"},"")
and returns
{"A", "B", "C", "D", "", "";
"A", "B", "C", "", "E", "";
"A", "B", "", "D", "E", "";
"A", "", "C", "D", "E", "";
"", "B", "C", "D", "E", "";
"A", "B", "C", "", "", "F";
"A", "B", "", "D", "", "F";
"A", "", "C", "D", "", "F";
"", "B", "C", "D", "", "F";
"A", "B", "", "", "E", "F";
"A", "", "C", "", "E", "F";
"", "B", "C", "", "E", "F";
"A", "", "", "D", "E", "F";
"", "B", "", "D", "E", "F";
"", "", "C", "D", "E", "F"}
Step 9 - Simplify formula
The LET function lets you  name intermediate calculation results which can shorten formulas considerably and improve performance.
LET(name1, name_value1, calculation_or_name2,
[name_value2, calculation_or_name3...])
IF(FILTER(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),MMULT(MOD(INT((SEQUENCE(2^F2)-1)/2^SEQUENCE(,F2,0)),2),SEQUENCE(F2)^0)=F3),TRANSPOSE(C2:C7),"")
x - MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2)
y - F2
LET(y, F2, x, MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2), IF(FILTER(x, MMULT(x, SEQUENCE(y)^0)=F3), TRANSPOSE(C2:C7), ""))
6. Test combinations (Solver)
The Solver is an Excel feature that can test combinations in order to find the best combination based on a condition or criteria. This example shows parcel names in column B, weight in column C, and the value in column D.
Which combination of four parcels out of 11 has the highest value if the total weight is lower than or equal to 291?
Total weight formula in cell F16:
Total value formula in cell F17:
Explaining the total weight formula
Step 1 - Compare values
The equal sign is a logical operator that lets you check if a value is equal to another value, in this case, multiple values to a single value.
The Excel Solver changes the numbers, 1 or 0 (zero), in cells F3:F13. We use these values to calculate the total weight for each combination.
F3:F13=1
Step 2 - Control the order of operation
The parentheses lets you control the order of intermediate calculations, we want to compare F3:F13 to 1 before we multiply by C3:C13.
(F3:F13=1)
Step 3 - Multiply
The asterisk character lets you multiply values and arrays in an Excel formula.
(F3:F13=1)*C3:C13
Step 4 - Calculate a total
The SUMPRODUCT function calculates the product of corresponding values and then returns the sum of each multiplication.
SUMPRODUCT(array1, [array2], ...)
SUMPRODUCT((F3:F13=1)*C3:C13)
Setting up the Excel Solver
- Go to the tab "Data" on the ribbon.
- Press the left mouse button on the "Solver" button.
- Press the left mouse button on the arrow next to "Set Objective" and select cell F17. This value is F3:F13 multiplied by D3:D13 and then summarized.
- Press the left mouse button on the radio button named "Max" to select it. This lets the solver know that we are looking for a combination that returns the largest sum.
- Press with left mouse button on the arrow next to "By changing variable cells" and select cells F3:F13. These cells changes between 1 and 0 (zero).
- Press with the left mouse button on the "Add" button. A dialog box appears, this lets you apply constraints. Add the constraints shown in the image above specifiied below "Subject to the Constraints:".
- Change solving method to "Evolutionary".
- Press with the mouse on the check box "Make unconstrained variables Non-negative to enable it.
- Press with left mouse button on the "Solve" button to start.
- A dialog box appears after some time, press the left mouse button on the "OK" button.
Useful links
COMBIN function - Microsoft
COMBIN function
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The following article has a formula that contains the COMBIN function.
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Functions in 'Math and trigonometry' category
The COMBIN function function is one of many functions in the 'Math and trigonometry' category.
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3 Responses to “How to use the COMBIN function”
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hello there,
this was very useful to me, thanks!
btw, =LET(y, F2, x, MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2), IF(FILTER(x, MMULT(x, SEQUENCE(y)^0)=F3), TRANSPOSE(C2:C7), ""))
works with office 2021 too,
can the formula be changed so it do three more things?
a-read the array from a horizontal array
b-ignore the blanks cells, don't write them down
c-combine all cells into one like a-b-c-d, a-b-c-e and etc
Hello mr_t
works with office 2021 too
Thank you for telling me.
a-read the array from a horizontal array
Sure! The array values are in A1:F1:
=LET(y, F2, x, MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2), IF(FILTER(x, MMULT(x, SEQUENCE(y)^0)=F3), A1:F1, ""))
b-ignore the blanks cells, don't write them down. c-combine all cells into one like a-b-c-d, a-b-c-e and etc
=LET(y, F2, x, MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2), TEXTJOIN("-", TRUE,IF(FILTER(x, MMULT(x, SEQUENCE(y)^0)=F3), A1:F1, "")))
thanks oscar!
a-working good!
b-i still need it, because it'll save me time, i want to repeat the function, and i rather not write down the range each time, but to give it a fixed range, like a1:q1 and then "fill right"
c-wasn't working for me
this is what i used:
=LET(y, COUNTA(T2:AJ2), x, MOD(INT((SEQUENCE(2^y)-1)/2^SEQUENCE(, y, 0)), 2), TEXTJOIN("-", TRUE,IF(FILTER(x, MMULT(x, SEQUENCE(y)^0)=6), t2:aj2, "")))
and with what you wrote it gave me all in one line, and i need it to spill each combination to different cell vertically
1-2-3-4
1-2-4-5
1-2-4-6
and etc
is it possible?