如何分析序列做fft后的频谱成分，
 

如：
a=[9.3547 9.1690 4.1027 8.9365 0.5789 3.5287 8.1317 0.0986 1.3889 2.0277 1.9872 6.0379 2.7219 1.9881 0.1527 7.4679]

a =

Columns 1 through 11

9.3547 9.1690 4.1027 8.9365 0.5789 3.5287 8.1317 0.0986 1.3889 2.0277 1.9872

Columns 12 through 16

6.0379 2.7219 1.9881 0.1527 7.4679

>> b=fft(a)

b =

Columns 1 through 5

67.6731 17.7455 - 9.0089i 6.2209 - 7.0600i 16.4102 - 7.3715i -0.3299 + 5.8274i

Columns 6 through 10

7.8135 +11.1901i 8.6647 -11.4490i -10.1061 + 0.9809i -10.8357 -10.1061 - 0.9809i

Columns 11 through 15

8.6647 +11.4490i 7.8135 -11.1901i -0.3299 - 5.8274i 16.4102 + 7.3715i 6.2209 + 7.0600i

Column 16

17.7455 + 9.0089i
则从b(1)到b(16)分别代表的频率是多少？