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1 function y = polyval(c,x) |
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2 #Evaluate a polynomial. |
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3 # |
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4 #In octave, a polynomial is represented by it's coefficients (arranged |
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5 #in descending order). For example a vector c of length n+1 corresponds |
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6 #to the following nth order polynomial |
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7 # |
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8 # p(x) = c(1) x^n + ... + c(n) x + c(n+1). |
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9 # |
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10 #polyval(c,x) will evaluate the polynomial at the specified value of x. |
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11 # |
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12 #If x is a vector or matrix, the polynomial is evaluated at each of the |
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13 #elements of x. |
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14 # |
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15 #SEE ALSO: polyvalm, poly, roots, conv, deconv, residue, filter, |
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16 # polyderiv, polyinteg |
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17 |
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18 # Author: |
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19 # Tony Richardson |
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20 # amr@mpl.ucsd.edu |
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21 # June 1994 |
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22 |
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23 if(nargin != 2) |
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24 error("usage: polyval(c,x)"); |
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25 endif |
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26 |
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27 if(is_matrix(c)) |
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28 error("poly: first argument must be a vector."); |
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29 endif |
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30 |
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31 if(length(c) == 0) |
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32 y = c; |
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33 return; |
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34 endif |
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35 |
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36 n = length(c); |
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37 y = c(1)*ones(rows(x),columns(x)); |
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38 for index = 2:n |
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39 y = c(index) + x .* y; |
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40 endfor |
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41 endfunction |
