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1 function c=conv(a,b) |
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2 # |
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3 # usage: conv(a,b) |
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4 # |
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5 # Returns the convolution of vectors a and b. The resulting vector |
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6 # is of length(a)+length(b)-1. If a and b are polynomial coefficients |
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7 # conv(a,b) is equivalent to polynomial multiplication. |
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8 |
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9 # written by Gerhard Kircher on Aug 27, 1993 |
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10 # modified by KH (Kurt.Hornik@ci.tuwien.ac.at) on Dec 23, 1993. |
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11 |
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12 l_a = length(a); |
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13 l_b = length(b); |
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14 return_row = 0; |
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15 if (l_a > l_b) |
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16 if (rows(a) == 1) |
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17 return_row = 1; |
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18 endif |
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19 else |
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20 if (rows(b) == 1) |
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21 return_row = 1; |
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22 endif |
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23 endif |
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24 a = reshape(a, l_a, 1); |
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25 b = reshape(b, l_b, 1); |
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26 if (l_a == 1 || l_b == 1) |
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27 c = a * b; |
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28 else |
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29 l_c = l_a + l_b - 1; |
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30 a(l_c) = 0; |
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31 b(l_c) = 0; |
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32 c = ifft(fft(a) .* fft(b)); |
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33 if !( any(imag(a)) || any(imag(b)) ) |
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34 c = real(c); |
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35 endif |
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36 if !( any(a-round(a)) || any(b-round(b)) ) |
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37 c = round(c); |
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38 endif |
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39 endif |
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40 if (return_row == 1) |
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41 c = c'; |
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42 end |
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43 endfunction |
