【求助】ifft的使用问题

jww100

各位大侠，我是个菜鸟，现有一个频域转时域的ifft问题一直搞不懂，恳请指教

H11 =
(-3/4*w^4+1095/2*i*w^3+129500*w^2-14950000*i*w-747500000)/(3*w^6-2865*i*w^5-956750*w^4+158800000*i*w^3+14127500000*w^2-742500000000*i*w-24750000000000)

subs(H11,w,-pi:pi/50:pi)

ans =
  1.0e-004 *
  Columns 1 through 9
   0.3023 + 0.0095i   0.3023 + 0.0093i   0.3023 + 0.0091i   0.3023 + 0.0089i   0.3023 + 0.0088i   0.3023 + 0.0086i   0.3022 + 0.0084i   0.3022 + 0.0082i   0.3022 + 0.0080i
  Columns 10 through 18
   0.3022 + 0.0078i   0.3022 + 0.0076i   0.3022 + 0.0074i   0.3022 + 0.0072i   0.3022 + 0.0070i   0.3022 + 0.0068i   0.3022 + 0.0067i   0.3022 + 0.0065i   0.3021 + 0.0063i
  Columns 19 through 27
   0.3021 + 0.0061i   0.3021 + 0.0059i   0.3021 + 0.0057i   0.3021 + 0.0055i   0.3021 + 0.0053i   0.3021 + 0.0051i   0.3021 + 0.0049i   0.3021 + 0.0047i   0.3021 + 0.0046i
  Columns 28 through 36
   0.3021 + 0.0044i   0.3021 + 0.0042i   0.3021 + 0.0040i   0.3021 + 0.0038i   0.3021 + 0.0036i   0.3021 + 0.0034i   0.3021 + 0.0032i   0.3020 + 0.0030i   0.3020 + 0.0028i
  Columns 37 through 45
   0.3020 + 0.0027i   0.3020 + 0.0025i   0.3020 + 0.0023i   0.3020 + 0.0021i   0.3020 + 0.0019i   0.3020 + 0.0017i   0.3020 + 0.0015i   0.3020 + 0.0013i   0.3020 + 0.0011i
  Columns 46 through 54
   0.3020 + 0.0009i   0.3020 + 0.0008i   0.3020 + 0.0006i   0.3020 + 0.0004i   0.3020 + 0.0002i   0.3020             0.3020 - 0.0002i   0.3020 - 0.0004i   0.3020 - 0.0006i
  Columns 55 through 63
   0.3020 - 0.0008i   0.3020 - 0.0009i   0.3020 - 0.0011i   0.3020 - 0.0013i   0.3020 - 0.0015i   0.3020 - 0.0017i   0.3020 - 0.0019i   0.3020 - 0.0021i   0.3020 - 0.0023i
  Columns 64 through 72
   0.3020 - 0.0025i   0.3020 - 0.0027i   0.3020 - 0.0028i   0.3020 - 0.0030i   0.3021 - 0.0032i   0.3021 - 0.0034i   0.3021 - 0.0036i   0.3021 - 0.0038i   0.3021 - 0.0040i
  Columns 73 through 81
   0.3021 - 0.0042i   0.3021 - 0.0044i   0.3021 - 0.0046i   0.3021 - 0.0047i   0.3021 - 0.0049i   0.3021 - 0.0051i   0.3021 - 0.0053i   0.3021 - 0.0055i   0.3021 - 0.0057i
  Columns 82 through 90
   0.3021 - 0.0059i   0.3021 - 0.0061i   0.3021 - 0.0063i   0.3022 - 0.0065i   0.3022 - 0.0067i   0.3022 - 0.0068i   0.3022 - 0.0070i   0.3022 - 0.0072i   0.3022 - 0.0074i
  Columns 91 through 99
   0.3022 - 0.0076i   0.3022 - 0.0078i   0.3022 - 0.0080i   0.3022 - 0.0082i   0.3022 - 0.0084i   0.3023 - 0.0086i   0.3023 - 0.0088i   0.3023 - 0.0089i   0.3023 - 0.0091i
  Columns 100 through 101
   0.3023 - 0.0093i   0.3023 - 0.0095i


>> h11=ifft(H11)
??? Function 'ifft' is not defined for values of class 'sym'.

我想问问我这用ifft到底出了什么问题
有什么更好的方法吗？
感谢万分！

科技在线

使用之前最好要fft。请看help文件吧

yelv123

原帖由 jww100 于 2008-9-14 03:12 发表

                               
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各位大侠，我是个菜鸟，现有一个频域转时域的ifft问题一直搞不懂，恳请指教

H11 =
(-3/4*w^4+1095/2*i*w^3+129500*w^2-14950000*i*w-747500000)/(3*w^6-2865*i*w^5-956750*w^4+158800000*i*w^3+14127500000*w^2 ...

你的里面H11的结果在ifft计算时不是数组，任然是变量，ifft（ans）这样应该可以了吧。

jww100

感谢"yelv123"