Question

this is a Fourier descriptor for a set of points

a =

  -3.4173 - 7.1634i
   7.4589 + 0.1321i
   3.1190 - 2.1870i
  -7.1979 + 0.2863i
   5.9594 + 0.8209i
  -5.4295 -15.7931i
  -1.0957 + 3.7485i
   0.2657 - 4.1459i
   7.4644 - 0.9546i

i need to sum each pair , but when i use a(1) or a(1,1) it produces -3.4173 – 7.1634i
when i use abs(a(1)) or abs(a(1,1)) it also produces 7.9367 which does not make sense for me !

what i need is how to access each element of any pair individually so i get -3.4173 alone and – 7.1634i alone as well so i can do normalization on it !

Answer 1

You have an array of complex numbers, and what you want to do is access the real and imaginary parts of each number.

r = real(a);
i = imag(a);

will result in r and i containing real and imaginary parts of your descriptor respectively.

To understand the reason you get an answer that “doesn’t make any sense” from abs(a(1)), follow this link.