Set difference of two arrays
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Syntax
C = setdiff(A,B)
C = setdiff(A,B,setOrder)
C = setdiff(A,B,___,'rows')
C = setdiff(A,B,'rows',___)
[C,ia] =setdiff(___)
[C,ia] =setdiff(A,B,'legacy')
[C,ia]= setdiff(A,B,'rows','legacy')
Description
example
C = setdiff(A,B) returns the data in A that is not in B, with no repetitions. C is in sorted order.
If
AandBare tables or timetables, thensetdiffreturns the rows fromAthat are not inB. For timetables,setdifftakes row times into account to determine equality, and sorts the output timetableCby row times.
example
C = setdiff(A,B,setOrder) returns C in a specific order. setOrder can be 'sorted' or 'stable'.
C = setdiff(A,B,___,'rows') and C = setdiff(A,B,'rows',___)A and each row of B as single entities and return the rows from A that are not in B, with no repetitions. You must specify A and B and optionally can specify setOrder.
The 'rows' option does not support cell arrays, unless one of the inputs is either a categorical array or a datetime array.
example
[C,ia] =setdiff(___) also returns the index vector ia using any of the previous syntaxes.
Generally,
C = A(ia).If the
'rows'option is specified, thenC = A(ia,:).If
AandBare tables or timetables, thenC = A(ia,:).
example
[C,ia] =setdiff(A,B,'legacy') and [ preserve the behavior of the C,ia]= setdiff(A,B,'rows','legacy')setdiff function from R2012b and prior releases.
The 'legacy' option does not support categoricalarrays, datetime arrays, duration arrays, tables, or timetables.
Examples
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Difference of Two Vectors
Open Live Script
Define two vectors with values in common.
A = [3 6 2 1 5 1 1]; B = [2 4 6];
Find the values in A that are not in B.
C = setdiff(A,B)
C = 1×3 1 3 5Difference of Two Tables
Open Live Script
Define two tables with rows in common.
A = table([1:5]',['A';'B';'C';'D';'E'],logical([0;1;0;1;0]))
A=5×3 table Var1 Var2 Var3 ____ ____ _____ 1 A false 2 B true 3 C false 4 D true 5 E falseB = table([1:2:10]',['A';'C';'E';'G';'I'],logical(zeros(5,1)))
B=5×3 table Var1 Var2 Var3 ____ ____ _____ 1 A false 3 C false 5 E false 7 G false 9 I falseFind the rows in A that are not in B.
C = setdiff(A,B)
C=2×3 table Var1 Var2 Var3 ____ ____ _____ 2 B true 4 D true Difference of Two Vectors and Indices to Different Values
Open Live Script
Define two vectors with values in common.
A = [3 6 2 1 5 1 1]; B = [2 4 6];
Find the values in A that are not in B as well as the index vector ia, such that C = A(ia).
[C,ia] = setdiff(A,B)
C = 1×3 1 3 5ia = 3×1 4 1 5Difference of Two Tables and Indices to Different Rows
Open Live Script
Define a table, A, of gender, age, and height for five people.
A = table(['M';'M';'F';'M';'F'],[27;52;31;46;35],[74;68;64;61;64],...'VariableNames',{'Gender' 'Age' 'Height'},...'RowNames',{'Ted' 'Fred' 'Betty' 'Bob' 'Judy'})
A=5×3 table Gender Age Height ______ ___ ______ Ted M 27 74 Fred M 52 68 Betty F 31 64 Bob M 46 61 Judy F 35 64 Define a table, B, with the same variables as A.
B = table(['F';'M';'F';'F'],[64;68;62;58],[31;47;35;23],...'VariableNames',{'Gender' 'Height' 'Age'},...'RowNames',{'Meg' 'Joe' 'Beth' 'Amy'})
B=4×3 table Gender Height Age ______ ______ ___ Meg F 64 31 Joe M 68 47 Beth F 62 35 Amy F 58 23 Find the rows in A that are not in B, as well as the index vector ia, such that C = A(ia,:).
[C,ia] = setdiff(A,B)
C=4×3 table Gender Age Height ______ ___ ______ Judy F 35 64 Ted M 27 74 Bob M 46 61 Fred M 52 68 ia = 4×1 5 1 4 2The rows of C are in sorted order first by Gender and next by Age.
Difference of Rows in Two Matrices
Open Live Script
Define two matrices with rows in common.
A = [7 9 7; 0 0 0; 7 9 7; 5 5 5; 1 4 5];B = [0 0 0; 5 5 5];
Find the rows from A that are not in B as well as the index vector ia, such that C = A(ia,:).
[C,ia] = setdiff(A,B,'rows')C = 2×3 1 4 5 7 9 7ia = 2×1 5 1Difference of Two Vectors with Specified Output Order
Open Live Script
Use the setOrder argument to specify the ordering of the values in C.
Specify 'stable' or 'sorted' when the order of the values in C are important.
A = [3 6 2 1 5 1 1]; B = [2 4 6];[C,ia] = setdiff(A,B,'stable')C = 1×3 3 1 5ia = 3×1 1 4 5Alternatively, you can specify 'sorted' order.
[C,ia] = setdiff(A,B,'sorted')C = 1×3 1 3 5ia = 3×1 4 1 5Difference of Vectors Containing NaNs
Open Live Script
Define two vectors containing NaN.
A = [5 NaN NaN]; B = [5 NaN];
Find the set difference of A and B.
C = setdiff(A,B)
C = 1×2 NaN NaNsetdiff treats NaN values as distinct.
Cell Array of Character Vectors with Trailing White Space
Open Live Script
Create a cell array of character vectors, A.
A = {'dog','cat','fish','horse'};Create a cell array of character vectors, B, where some of the vectors have trailing white space.
B = {'dog ','cat','fish ','horse'};Find the character vectors in A that are not in B.
[C,ia] = setdiff(A,B)
C = 1x2 cell {'dog'} {'fish'}ia = 2×1 1 3setdiff treats trailing white space in cell arrays of character vectors as distinct characters.
Difference of Char and Cell Array of Character Vectors
Open Live Script
Create a character vector, A.
A = ['cat';'dog';'fox';'pig'];class(A)
ans = 'char'
Create a cell array of character vectors, B.
B={'dog','cat','fish','horse'};class(B)ans = 'cell'
Find the character vectors in A that are not in B.
C = setdiff(A,B)
C = 2x1 cell {'fox'} {'pig'}The result, C, is a cell array of character vectors.
class(C)
ans = 'cell'
Preserve Legacy Behavior of setdiff
Open Live Script
Use the 'legacy' flag to preserve the behavior of setdiff from R2012b and prior releases in your code.
Find the difference of A and B with the current behavior.
A = [3 6 2 1 5 1 1]; B = [2 4 6];[C1,ia1] = setdiff(A,B)
C1 = 1×3 1 3 5ia1 = 3×1 4 1 5Find the difference of A and B, and preserve the legacy behavior.
[C2,ia2] = setdiff(A,B,'legacy')C2 = 1×3 1 3 5ia2 = 1×3 7 1 5Input Arguments
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setOrder — Order flag
'sorted' (default) | 'stable'
Order flag, specified as 'sorted' or 'stable', indicates the order of the values (or rows) in C.
| Flag | Description |
|---|---|
'sorted' | The values (or rows) in Example C = setdiff([4 1 3 2 5],[2 1],'sorted')C = 3 4 5 |
'stable' | The values (or rows) in Example C = setdiff([4 1 3 2 5],[2 1],'stable')C = 4 3 5 |
Data Types: char | string
Output Arguments
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C — Difference of A and B
vector | matrix | table | timetable
Difference of A and B, returned as a vector, matrix, table, or timetable. If the inputs A and B are tables or timetables, then the order of the variables in C is the same as the order of the variables in A.
The following describes the shape of C when the inputs are vectors or matrices and when the 'legacy' flag is not specified:
If the
'rows'flag is not specified andAis a row vector, thenCis a row vector.If the
'rows'flag is not specified andAis not a row vector, thenCis a column vector.If the
'rows'flag is specified, thenCis a matrix containing the rows ofAthat are not inB.If all the values (or rows) of
Aare also inB, thenCis an empty matrix.
The class of C is the same as the class of A, unless:
Ais a character array andBis a cell array of character vectors, in which caseCis a cell array of character vectors.Ais a character vector, cell array of character vectors, or string, andBis a categorical array, in which caseCis a categorical array.Ais a cell array of character vectors or single character vector andBis a datetime array, in which caseCis a datetime array.Ais a character vector or cell array of character vectors andBis a string array, in which caseCis a string array.
ia — Index to A
column vector
Index to A, returned as a column vector when the 'legacy' flag is not specified. ia identifies the values (or rows) in A that are not in B. If there is a repeated value (or row) appearing exclusively in A, then ia contains the index to the first occurrence of the value (or row).
Tips
To find the set difference with respect to a subset of variables from a table or timetable, you can use column subscripting. For example, you can use
setdiff(A(:,, wherevars),B(:,vars))varsis a positive integer, a vector of positive integers, a variable name, a cell array of variable names, or a logical vector. Alternatively, you can use vartype to create a subscript that selects variables of a specified type.
Extended Capabilities
Tall Arrays
Calculate with arrays that have more rows than fit in memory.
Usage notes and limitations:
The
'stable'and'legacy'options are not supported.Inputs of type
'char'are not supported.Ordinal categorical arrays are not supported.
For more information, see Tall Arrays.
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
Code generation does not support cell arrays for the first or second arguments.
When you do not specify the
'rows'option:Inputs
AandBmust be vectors. If you specify the'legacy'option, then inputsAandBmust be row vectors.The first dimension of a variable-size row vector must have fixed length 1. The second dimension of a variable-size column vector must have fixed length 1.
Do not use
[]to represent the empty set. Use a 1-by-0 or 0-by-1 input, for example,zeros(1,0), to represent the empty set.If you specify the
'legacy'option, then empty outputs are row vectors, 1-by-0. They are never 0-by-0.
When you specify both the
'legacy'and'rows'options, the outputiais a column vector. Ifiais empty, then it is 0-by-1. It is never 0-by-0, even if the outputCis 0-by-0.When the
setOrderis not'stable'or when you specify the'legacy'option, the inputs must already be sorted in ascending order. The first output,C, is sorted in ascending order.Complex inputs must be
singleordouble.When one input is complex and the other input is real, do one of the following:
Set
setOrderto'stable'.Sort the real input in complex ascending order (by absolute value). Suppose the real input is
x. Usesort(complex(x))orsortrows(complex(x)).
See Code Generation for Complex Data with Zero-Valued Imaginary Parts (MATLAB Coder).
Thread-Based Environment
Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.
This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
Usage notes and limitations:
The
'legacy'flag is not supported.64-bit integers are not supported.
For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).
Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.
Usage notes and limitations:
The
'legacy'flag is not supported.Table, timetable, categorical, datetime and duration inputs are not supported.
Inputs of type
charandstringare not supported whenAorBis a cell array of character vectors. Convert cell arrays of character vectors input arguments to string arrays instead.
For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).
Version History
Introduced before R2006a
See Also
unique | intersect | ismember | issorted | union | setxor | sort
Topics
- Combine Categorical Arrays
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