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POReading C code written for R packages. Where to find definitions for RANDIN, UNIF, EPS, etc?
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  1. POReading C code written for R packages. Where to find definitions for RANDIN, UNIF, EPS, etc?
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    copied!<p>I am interested in precisely understanding C code for R packages. But I have come across code such as <code>RANDIN</code>, <code>RANDOUT</code>, <code>UNIF</code>, <code>EPS</code> etc (are they macros?) for which I don't know where to find the implementations/definitions.</p> <p>Where can I find the code (and explanations if any) for these capitalised 'expressions'?</p> <p>An example is the <code>VR_onlineSOM</code> function inside the 'class' R package. This function has the following code written in C:</p> <pre><code>void VR_onlineSOM(double *data, double *codes, double *nhbrdist, double *alpha, double *radii, Sint *pn, Sint *pp, Sint *pncodes, Sint *rlen) { int n = *pn, p = *pp, ncodes = *pncodes; int i, j, k, nearest = 0 /* -Wall */, nind; double dm, dist, tmp; unsigned int cd; /* avoid spurious warning from gcc pre-4.3.0 */ RANDIN; for (k = 0; k &lt; *rlen; k++) { /* pick a random data point */ i = (int)(n * UNIF); /* find the nearest code 'near' */ nind = 0; dm = DOUBLE_XMAX; for (cd = 0; cd &lt; ncodes; cd++) { dist = 0.0; for (j = 0; j &lt; p; j++) { tmp = data[i + j*n] - codes[cd + j*ncodes]; dist += tmp * tmp; } if (dist &lt;= dm * (1 + EPS)) { if (dist &lt; dm * (1 - EPS)) { nind = 0; nearest = cd; } else { if(++nind * UNIF &lt; 1.0) nearest = cd; } dm = dist; } /* update all codes within radii[k] of 'nearest' */ for (cd = 0; cd &lt; ncodes; cd++) { if(nhbrdist[cd + ncodes*nearest] &gt; radii[k]) continue; for(j = 0; j &lt; p; j++) codes[cd + j*ncodes] += alpha[k] * (data[i + j*n] - codes[cd + j*ncodes]); } } } RANDOUT; } </code></pre>
 

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