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1 | // -*- C++ -*- |
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2 | // $Id$ |
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3 | |
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4 | /* |
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5 | * Chi^2 distribution |
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6 | * |
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7 | * This code has been adapted from RANDLIB.C 1.3, by |
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8 | * Barry W. Brown, James Lovato, Kathy Russell, and John Venier. |
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9 | * Code was originally by Ahrens and Dieter (see above). |
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10 | * |
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11 | * Adapter's notes: |
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12 | */ |
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13 | |
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14 | #ifndef BZ_RANDOM_CHISQUARE |
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15 | #define BZ_RANDOM_CHISQUARE |
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16 | |
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17 | #ifndef BZ_RANDOM_GAMMA |
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18 | #include <random/gamma.h> |
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19 | #endif |
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20 | |
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21 | BZ_NAMESPACE(ranlib) |
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22 | |
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23 | template<typename T = double, typename IRNG = defaultIRNG, |
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24 | typename stateTag = defaultState> |
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25 | class ChiSquare : public Gamma<T,IRNG,stateTag> |
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26 | { |
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27 | public: |
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28 | typedef T T_numtype; |
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29 | |
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30 | ChiSquare(T df) |
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31 | : Gamma<T,IRNG,stateTag>(df/2.0) // isn't this redundant with setDF call? |
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32 | { |
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33 | setDF(df); |
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34 | } |
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35 | |
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36 | ChiSquare(T df, unsigned int i) |
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37 | : Gamma<T,IRNG,stateTag>(df/2.0, i) |
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38 | { |
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39 | setDF(df); |
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40 | } |
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41 | |
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42 | void setDF(T _df) |
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43 | { |
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44 | BZPRECONDITION(_df > 0.0); |
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45 | df = _df; |
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46 | Gamma<T,IRNG,stateTag>::setMean(df/2.0); |
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47 | } |
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48 | |
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49 | T random() |
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50 | { |
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51 | return 2.0 * sgamma(); |
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52 | } |
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53 | |
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54 | protected: |
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55 | T sgamma() |
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56 | { |
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57 | return Gamma<T,IRNG,stateTag>::random(); |
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58 | } |
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59 | |
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60 | T df; |
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61 | }; |
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62 | |
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63 | BZ_NAMESPACE_END |
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64 | |
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65 | #endif // BZ_RANDOM_CHISQUARE |
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