Documentation

eye

Create identity matrix with fixed-point properties

Syntax

I = eye('like',p)
I = eye(n,'like',p)
I = eye(n,m,'like',p)
I = eye(sz,'like',p)

Description

I = eye('like',p) returns the scalar 1 with the same fixed-point properties and complexity (real or complex) as the prototype argument, p. The output, I, contains the same numerictype and fimath properties as p.

example

I = eye(n,'like',p) returns an n-by-n identity matrix like p, with ones on the main diagonal and zeros elsewhere.

example

I = eye(n,m,'like',p) returns an n-by-m identity matrix like p.

I = eye(sz,'like',p) returns an array like p, where the size vector, sz, defines size(I).

Examples

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Create a prototype fi object, p.

p = fi([],1,16,14);

Create a 3-by-4 identity matrix with the same fixed-point properties as p.

I = eye(3,4,'like',p)
I = 

     1     0     0     0
     0     1     0     0
     0     0     1     0

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 14

Create a signed fi object with word length of 16, fraction length of 15 and OverflowAction set to Wrap.

format long
p = fi([],1,16,15,'OverflowAction','Wrap');

Create a 2-by-2 identity matrix with the same numerictype properties as p.

X = eye(2,'like',p)
X = 

   0.999969482421875                   0
                   0   0.999969482421875

          DataTypeMode: Fixed-point: binary point scaling
            Signedness: Signed
            WordLength: 16
        FractionLength: 15

        RoundingMethod: Nearest
        OverflowAction: Wrap
           ProductMode: FullPrecision
               SumMode: FullPrecision

1 cannot be represented by the data type of p, so the value saturates. The output fi object X has the same numerictype and fimath properties as p.

Input Arguments

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Size of first dimension of I, specified as an integer value.

  • If n is the only integer input argument, then I is a square n-by-n identity matrix.

  • If n is 0, then I is an empty matrix.

  • If n is negative, then it is treated as 0.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Size of second dimension of I, specified as an integer value.

  • If m is 0, then I is an empty matrix.

  • If m is negative, then it is treated as 0.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Size of I, specified as a row vector of no more than two integer values.

  • If an element of sz is 0, then I is an empty matrix.

  • If an element of sz is negative, then the element is treated as 0.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Prototype, specified as a fi object or numeric variable.

If the value 1 overflows the numeric type of p, the output saturates regardless of the specified OverflowAction property of the attached fimath. All subsequent operations performed on the output obey the rules of the attached fimath.

Data Types: fi | single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Tips

Using the b = cast(a,'like',p) syntax to specify data types separately from algorithm code allows you to:

  • Reuse your algorithm code with different data types.

  • Keep your algorithm uncluttered with data type specifications and switch statements for different data types.

  • Improve readability of your algorithm code.

  • Switch between fixed-point and floating-point data types to compare baselines.

  • Switch between variations of fixed-point settings without changing the algorithm code.

Introduced in R2015a

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