Define a vector of double integer values and calculate the exponents for the next power of 2 higher than those values.

a = [1 -2 3 -4 5 9 519];
p = nextpow2(a)

p = 1×7

     0     1     2     2     3     4    10

Calculate the positive next powers of 2.

np2 = 2.^p

np2 = 1×7

           1           2           4           4           8          16        1024

Preserve the sign of the original input values.

np2.*sign(a)

ans = 1×7

           1          -2           4          -4           8          16        1024

Define a vector of unsigned integers and calculate the exponents for the next power of 2 higher than those values.

a = uint32([1020 4000 32700]);
p = nextpow2(a)

p = 1x3 uint32 row vector

   10   12   15

Calculate the next powers of 2 higher than the values in a.

2.^p

ans = 1x3 uint32 row vector

    1024    4096   32768

Use the nextpow2 function to increase the performance of fft when the length of a signal is not a power of 2.

Create a 1-D vector containing 8191 sample values.

rng default;
x = rand([1,8191]);

Calculate the next power of 2 higher than 8191.

p = nextpow2(8191);
n = 2^p

n = 8192

Pass the signal and the next power of 2 to the fft function.

y = fft(x,n);