1 | /* compile with: cmex sample_hist.c util.o -lm |
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2 | * |
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3 | * Each column of p is a distribution which is sampled from n times. |
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4 | * Requires all(col_sum(p) == 1). |
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5 | */ |
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6 | #include "mex.h" |
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7 | #include "util.h" |
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8 | |
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9 | void MultiRand(double *p, int len, int n, double *result) |
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10 | { |
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11 | double z = 1; |
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12 | int i; |
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13 | for(i=1;i<len;i++) { |
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14 | int r = BinoRand(*p/z, n); |
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15 | *result++ = r; |
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16 | n -= r; |
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17 | z -= *p; |
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18 | if(z == 0) { |
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19 | memset(result, 0, (len-i)*sizeof(double)); |
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20 | return; |
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21 | } |
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22 | p++; |
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23 | } |
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24 | *result = n; |
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25 | } |
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26 | |
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27 | void mexFunction(int nlhs, mxArray *plhs[], |
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28 | int nrhs, const mxArray *prhs[]) |
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29 | { |
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30 | int rows, cols, n, i; |
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31 | double *p, *r; |
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32 | |
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33 | if(nrhs != 2) |
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34 | mexErrMsgTxt("Usage: h = sample_hist(p, n)"); |
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35 | |
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36 | /* prhs[0] is first argument. |
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37 | * mxGetPr returns double* (data, col-major) |
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38 | * mxGetM returns int (rows) |
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39 | * mxGetN returns int (cols) |
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40 | */ |
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41 | rows = mxGetM(prhs[0]); |
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42 | cols = mxGetN(prhs[0]); |
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43 | p = mxGetPr(prhs[0]); |
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44 | n = (int)*mxGetPr(prhs[1]); |
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45 | if(mxGetM(prhs[1]) != 1 || mxGetN(prhs[1]) != 1) |
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46 | mexErrMsgTxt("n must be scalar"); |
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47 | |
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48 | if(mxIsSparse(prhs[0])) |
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49 | mexErrMsgTxt("Cannot handle sparse matrices. Sorry."); |
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50 | |
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51 | /* plhs[0] is first output */ |
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52 | plhs[0] = mxCreateDoubleMatrix(rows, cols, mxREAL); |
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53 | r = mxGetPr(plhs[0]); |
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54 | for(i=0;i<cols;i++) { |
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55 | MultiRand(p, rows, n, r); |
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56 | p += rows; |
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57 | r += rows; |
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58 | } |
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59 | } |
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60 | |
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