bitrevorder

Permute data into bit-reversed order

Syntax

y = bitrevorder(x)

[y,i] = bitrevorder(x)

Description

y = bitrevorder(x) returns the input data in bit-reversed order.

[y,i] = bitrevorder(x) also returns the bit-reversed indices, i, such that y = x(i).

Examples

Vector in Bit-Reversed Order

Create a column vector and obtain its bit-reversed version. Verify by displaying the binary representation explicitly.

x = (0:15)';
v = bitrevorder(x);

x_bin = dec2bin(x);
v_bin = dec2bin(v);

T = table(x,x_bin,v,v_bin)

T=16×4 table
    x     x_bin    v     v_bin
    __    _____    __    _____

     0    0000      0    0000 
     1    0001      8    1000 
     2    0010      4    0100 
     3    0011     12    1100 
     4    0100      2    0010 
     5    0101     10    1010 
     6    0110      6    0110 
     7    0111     14    1110 
     8    1000      1    0001 
     9    1001      9    1001 
    10    1010      5    0101 
    11    1011     13    1101 
    12    1100      3    0011 
    13    1101     11    1011 
    14    1110      7    0111 
    15    1111     15    1111 

Input Arguments

x — Input data

vector | matrix

Input data, specified as a vector or matrix. The length or number of rows of x must be an integer power of 2. If x is a matrix, the bit-reversal occurs on the first dimension of x with size greater than 1.

Data Types: single | double
Complex Number Support: Yes

Output Arguments

y — Bit-reversed data

vector | matrix

Bit-reversed data, returned as a vector or matrix. y is the same size as x.

i — Bit-reversed indices

vector | matrix

Bit-reversed indices, returned as a vector or matrix such that y = x(i). MATLAB^® matrices use 1-based indexing, so the first index of y is 1, not 0.

More About

Bit-Reversed Ordering

bitrevorder is useful for prearranging filter coefficients so that bit-reversed ordering does not have to be performed as part of an fft or ifft computation.

Bit-reversed ordering can improve run-time efficiency for external applications or for Simulink^® blockset models. Both MATLAB fft and ifft functions process linear input and output.

Note

Using bitrevorder is equivalent to using digitrevorder with radix base 2.

This table shows the numbers 0 through 7, the corresponding bits, and the bit-reversed numbers.

Linear Index	Bits	Bit-Reversed	Bit-Reversed Index
0	000	000	0
1	001	100	4
2	010	010	2
3	011	110	6
4	100	001	1
5	101	101	5
6	110	011	3
7	111	111	7

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a