# What is the best way to count the occurrences of two table columns together?

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Monika Jaskolka
on 17 Mar 2021

Commented: Monika Jaskolka
on 17 Mar 2021

I have a table that looks like this:

>> A = {'A'; 'B'; 'C'; 'A'; 'C'; 'C'; 'B'};

>> B = {'x'; 'y'; 'z'; 'xx'; 'z'; 'z'; 'y'};

>> T = table(A,B)

T =

A B

___ ____

'A' 'x'

'B' 'y'

'C' 'z'

'A' 'xx'

'C' 'z'

'C' 'z'

'B' 'y'

What is the best way of getting a result like the one blelow? I essentially want to count the occurrances of column A and B., and have as output a table.

ans =

A B occ

____ ____ ____

'A' 'x' 1

'A' 'xx' 1

'B' 'y' 2

'C' 'z' 3

The immediate solution that comes to mind is to combine the table columns together, and then use histc, but is there a better approach that will leave me with a Table where A and B aren't combined? Or is usng a strsplit on T2.AB the way to go?

>> c = strcat(T.A, ',', T.B)

c =

7×1 cell array

'A,x'

'B,y'

'C,z'

'A,xx'

'C,z'

'C,z'

'B,y'

>> [AB, ~, J] = unique(c);

>> occ = histc(J, 1:numel(AB));

>> T2 = table(AB, occ)

T2 =

AB occ

______ ___

'A,x' 1

'A,xx' 1

'B,y' 2

'C,z' 3

##### 0 Comments

### Accepted Answer

Star Strider
on 17 Mar 2021

Try this:

A = {'A'; 'B'; 'C'; 'A'; 'C'; 'C'; 'B'};

B = {'x'; 'y'; 'z'; 'xx'; 'z'; 'z'; 'y'};

T = table(A,B);

[Tu,~,ix] = unique(T, 'rows', 'stable');

Tally = accumarray(ix, 1);

TallyTable = [Tu, table(Tally)]

producing:

TallyTable =

4×3 table

A B Tally

_____ ______ _____

{'A'} {'x' } 1

{'B'} {'y' } 2

{'C'} {'z' } 3

{'A'} {'xx'} 1

##### 0 Comments

### More Answers (2)

Steve Eddins
on 17 Mar 2021

In my previous answer, I forgot that grpstats is in the Statistics and Machine Learning Toolbox. Here is an answer using groupsummary, which is in MATLAB.

>> groupsummary(T,["A" "B"])

ans =

4×3 table

A B GroupCount

___ ____ __________

"A" "x" 1

"A" "xx" 1

"B" "y" 2

"C" "z" 3

Steve Eddins
on 17 Mar 2021

I think grpstats will do what you want:

>> grpstats(T,["A" "B"])

ans =

4×3 table

A B GroupCount

_____ ______ __________

A_x {'A'} {'x' } 1

A_xx {'A'} {'xx'} 1

B_y {'B'} {'y' } 2

C_z {'C'} {'z' } 3

Also, tabular text analysis will generally be more efficient and easier to perform if you work with strings instead of cell arrays of char vectors:

>> A = ["A" ; "B" ; "C" ; "A" ; "C" ; "C" ; "B" ]

A =

7×1 string array

"A"

"B"

"C"

"A"

"C"

"C"

"B"

>> B = ["x" ; "y" ; "z" ; "xx" ; "z" ; "z" ; "y" ]

B =

7×1 string array

"x"

"y"

"z"

"xx"

"z"

"z"

"y"

>> T = table(A,B)

T =

7×2 table

A B

___ ____

"A" "x"

"B" "y"

"C" "z"

"A" "xx"

"C" "z"

"C" "z"

"B" "y"

>> grpstats(T,["A" "B"])

ans =

4×3 table

A B GroupCount

___ ____ __________

A_x "A" "x" 1

A_xx "A" "xx" 1

B_y "B" "y" 2

C_z "C" "z" 3

##### 1 Comment

Steve Eddins
on 17 Mar 2021

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