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eq, ==

Determine equality



A == B returns a logical array with elements set to logical 1 (true) where arrays 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 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.


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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 = categorical({'heads' 'heads' 'tails'; 'tails' 'heads' 'tails'})
A = 2x3 categorical
     heads      heads      tails 
     tails      heads      tails 

Find all values in the 'heads' category.

A == 'heads'
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

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

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

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.

ans = 2x1 logical array


Input Arguments

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Operands, specified as scalars, vectors, matrices, or multidimensional arrays. 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.

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


  • 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.

Extended Capabilities

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Version History

Introduced before R2006a

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