# eq, ==

Determine equality

## Description

example

A == B returns a logical array or a table of logical values with elements set to logical 1 (true) where inputs A and B are equal; otherwise, the element is logical 0 (false). The test compares both real and imaginary parts of numeric arrays. eq returns logical 0 (false) where A or B have missing values, such as NaN or undefined categorical elements.

eq(A,B) is an alternative way to execute A == B, but is rarely used. It enables operator overloading for classes.

## Examples

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Create two vectors containing both real and imaginary numbers, then compare the vectors for equality.

A = [1+i 3 2 4+i];
B = [1 3+i 2 4+i];
A == B
ans = 1x4 logical array

0   0   1   1

The eq function tests both real and imaginary parts for equality, and returns logical 1 (true) only where both parts are equal.

Create a character vector.

M = 'magenta';

Test for the presence of a specific character using ==.

M == 'e'
ans = 1x7 logical array

0   0   0   1   0   0   0

The value of logical 1 (true) indicates the presence of the character 'e'.

Create a categorical array with two values: 'heads' and 'tails'.

A = 2x3 categorical

Find all values in the 'heads' category.

ans = 2x3 logical array

1   1   0
0   1   0

A value of logical 1 (true) indicates a value in the category.

Compare the rows of A for equality.

A(1,:) == A(2,:)
ans = 1x3 logical array

0   1   1

A value of logical 1 (true) indicates where the rows have equal category values.

Many numbers expressed in decimal text cannot be represented exactly as binary floating numbers. This leads to small differences in results that the == operator reflects.

Perform a few subtraction operations on numbers expressed in decimal and store the result in C.

C = 0.5-0.4-0.1
C = -2.7756e-17

With exact decimal arithmetic, C should be equal to exactly 0. Its small value is due to the nature of binary floating-point arithmetic.

Compare C to 0 for equality.

C == 0
ans = logical
0

Compare floating-point numbers using a tolerance, tol, instead of using ==.

tol = eps(0.5);
abs(C-0) < tol
ans = logical
1

The two numbers, C and 0, are closer to one another than two consecutive floating-point numbers near 0.5. In many situations, C may act like 0.

Compare the elements of two datetime arrays.

Create two datetime arrays in different time zones.

t1 = [2014,04,14,9,0,0;2014,04,14,10,0,0];
A = datetime(t1,'TimeZone','America/Los_Angeles');
A.Format = 'd-MMM-y HH:mm:ss Z'
A = 2x1 datetime
14-Apr-2014 09:00:00 -0700
14-Apr-2014 10:00:00 -0700

t2 = [2014,04,14,12,0,0;2014,04,14,12,30,0];
B = datetime(t2,'TimeZone','America/New_York');
B.Format = 'd-MMM-y HH:mm:ss Z'
B = 2x1 datetime
14-Apr-2014 12:00:00 -0400
14-Apr-2014 12:30:00 -0400

Check where elements in A and B are equal.

A==B
ans = 2x1 logical array

1
0

Since R2023a

Create two tables and compare them. The row names (if present in both) and variable names must be the same, but do not need to be in the same orders. Rows and variables of the output are in the same orders as the first input.

A = table([1;2],[3;4],VariableNames=["V1","V2"],RowNames=["R1","R2"])
A=2×2 table
V1    V2
__    __

R1    1     3
R2    2     4

B = table([4;2],[3;1],VariableNames=["V2","V1"],RowNames=["R2","R1"])
B=2×2 table
V2    V1
__    __

R2    4     3
R1    2     1

A == B
ans=2×2 table
V1       V2
_____    _____

R1    true     false
R2    false    true

## Input Arguments

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Operands, specified as scalars, vectors, matrices, multidimensional arrays, tables, or timetables. Inputs A and B must either be the same size or have sizes that are compatible (for example, A is an M-by-N matrix and B is a scalar or 1-by-N row vector). For more information, see Compatible Array Sizes for Basic Operations.

You can compare numeric inputs of any type, and the comparison does not suffer loss of precision due to type conversion.

• If one input is a categorical array, the other input can be a categorical array, a cell array of character vectors, or a single character vector. A single character vector expands into a cell array of character vectors of the same size as the other input. If both inputs are ordinal categorical arrays, they must have the same sets of categories, including their order. If both inputs are categorical arrays that are not ordinal, they can have different sets of categories. See Compare Categorical Array Elements for more details.

• If one input is a datetime array, the other input can be a datetime array, a character vector, or a cell array of character vectors.

• If one input is a duration array, the other input can be a duration array or a numeric array. The operator treats each numeric value as a number of standard 24-hour days.

• If one input is a string array, the other input can be a string array, a character vector, or a cell array of character vectors. The corresponding elements of A and B are compared lexicographically.

Inputs that are tables or timetables must meet the following conditions: (since R2023a)

• If an input is a table or timetable, then all its variables must have data types that support the operation.

• If only one input is a table or timetable, then the other input must be a numeric or logical array.

• If both inputs are tables or timetables, then:

• Both inputs must have the same size, or one of them must be a one-row table.

• Both inputs must have variables with the same names. However, the variables in each input can be in a different order.

• If both inputs are tables and they both have row names, then their row names must be the same. However, the row names in each input can be in a different order.

• If both inputs are timetables, then their row times must be the same. However, the row times in each input can be in a different order.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | categorical | datetime | duration | table | timetable
Complex Number Support: Yes

## Tips

• When comparing handle objects, use == to test whether objects have the same handle. Use isequal to determine if objects with different handles have equal property values.

## Version History

Introduced before R2006a

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