Define a vector with a repeated value.

A = [9 2 9 5];

Find the unique values ofA.

C = unique(A)

C =1×32 5 9

Create a table with some repeated data.

Name = {'Fred';'Betty';'Bob';'George';'Jane'}; Age = [38;43;38;40;38]; Height = [71;69;64;67;64]; Weight = [176;163;131;185;131]; A = table(Age,Height,Weight,'RowNames',Name)

A=5×3 tableAge Height Weight ___ ______ ______ Fred 38 71 176 Betty 43 69 163 Bob 38 64 131 George 40 67 185 Jane 38 64 131

Find the unique rows ofA.uniquereturns the rows ofAin sorted order by the first variableAgeand then by the second variableHeight.

C = unique(A)

C=4×3 tableAge Height Weight ___ ______ ______ Bob 38 64 131 Fred 38 71 176 George 40 67 185 Betty 43 69 163

Find the table rows with unique values in the first variableAge. If you only want one table variable to contain unique values, you can use the indices returned byuniqueto extract those rows from the table.

[C,ia] = unique(A.Age); B = A(ia,:)

B=3×3 tableAge Height Weight ___ ______ ______ Fred 38 71 176 George 40 67 185 Betty 43 69 163

Define a vector with a repeated value.

A = [9 2 9 5];

Find the unique values ofAand the index vectorsiaandic, such thatC = A(ia)andA = C(ic).

[C, ia, ic] = unique(A)

C =1×32 5 9

ia =3×12 4 1

ic =4×13 1 3 2

Create a 10-by-3 matrix with some repeated rows.

A = randi(3,10,3)

A =10×33 1 2 3 3 1 1 3 3 3 2 3 2 3 3 1 1 3 1 2 3 2 3 2 3 3 2 3 3 1

Find the unique rows ofAbased on the data in the first two columns. Specify three outputs to return the index vectorsiaandic.

[C,ia,ic] = unique(A(:,1:2),'rows')

C =7×21 1 1 2 1 3 2 3 3 1 3 2 3 3

ia =7×16 7 3 5 1 4 2

ic =10×15 7 3 6 4 1 2 4 7 7

Useiato index intoAand retrieve the rows that have unique combinations of elements in the first two columns.

uA = A(ia,:)

uA =7×31 1 3 1 2 3 1 3 3 2 3 3 3 1 2 3 2 3 3 3 1

Find the unique elements in a vector and then useaccumarrayto count the number of times each unique element appears.

Create a vector of random integers from 1 through 5.

a = randi([1 5],200,1);

Find the unique elements in the vector. Return the index vectorsiaandic.

[C,ia,ic] = unique(a);

Count the number of times each element inCappears ina. Specifyicas the first input toaccumarrayand1as the second input so that the function counts repeated subscripts inic. Summarize the results.

a_counts = accumarray(ic,1); value_counts = [C, a_counts]

value_counts =5×21 46 2 36 3 38 4 39 5 41

Use thesetOrderargument to specify the ordering of the values inC.

Specify'stable'if you want the values inCto have the same order as inA.

A = [9 2 9 5]; [C, ia, ic] = unique(A,'stable')

C =1×39 2 5

ia =3×11 2 4

ic =4×11 2 1 3

Alternatively, you can specify'sorted'order.

[C, ia, ic] = unique(A,'sorted')

C =1×32 5 9

ia =3×12 4 1

ic =4×13 1 3 2

Define a vector containingNaN.

A = [5 5 NaN NaN];

Find the unique values ofA.

C = unique(A)

C =1×35 NaN NaN

uniquetreatsNaNvalues as distinct.

Create a vectorx. Obtain a second vectoryby transforming and untransformingx. This transformation introduces round-off differences iny.

x = (1:6)'*pi; y = 10.^log10(x);

Verify thatxandyare not identical by taking the difference.

x-y

ans =6×110-14× 0.0444 0 0 0 0 -0.3553

Useuniqueto find the unique elements in the concatenated vector[x;y]. Theuniquefunction performs exact comparisons and determines that some values inxare not exactly equal to values iny. These are the same elements that have a nonzero difference inx-y. Thus,ccontains values thatappearto be duplicates.

c = unique([x;y])

c =8×13.1416 3.1416 6.2832 9.4248 12.5664 15.7080 18.8496 18.8496

Useuniquetolto perform the comparison using a small tolerance.uniquetoltreats elements that are within tolerance as equal.

C = uniquetol([x;y])

C =6×13.1416 6.2832 9.4248 12.5664 15.7080 18.8496

Create a cell array of character vectors.

A = {'one','two','twenty-two','One','two'};

Find the unique character vectors contained inA.

C = unique(A)

C =1x4 cell array{'One'} {'one'} {'twenty-two'} {'two'}

Create a cell array of character vectors,A, where some of the vectors have trailing white space.

A = {'dog','cat','fish','horse','dog ','fish '};

Find the unique character vectors contained inA.

C = unique(A)

C =1x6 cell array{'cat'} {'dog'} {'dog '} {'fish'} {'fish '} {'horse'}

uniquetreats trailing white space in cell arrays of character vectors as distinct characters.

Use the'legacy'flag to preserve the behavior ofuniquefrom R2012b and prior releases in your code.

Find the unique elements ofAwith the current behavior.

A = [9 2 9 5]; [C1, ia1, ic1] = unique(A)

C1 =1×32 5 9

ia1 =3×12 4 1

ic1 =4×13 1 3 2

Find the unique elements ofA, and preserve the legacy behavior.

[C2, ia2, ic2] = unique(A,'legacy')

C2 =1×32 5 9

ia2 =1×32 4 3

ic2 =1×43 1 3 2