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esl_hyperexp.c
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/* Statistical routines for hyperexponential distributions.
*
* Contents:
* 1. The ESL_HYPEREXP object
* 2. Evaluating densities and distributions
* 3. Generic API routines: for general interface w/ histogram module
* 4. Dumping plots for files
* 5. Sampling
* 6. File input
* 7. ML fitting to complete data
* 8. ML fitting to binned data
* 9. Test driver
* 10. Example
*
* Xrefs:
* STL9/140 : original implementation
* STL9/143-144 : ML fitting to binned data
*
* To-do:
* - Fit*() functions should return eslEINVAL on n=0, eslENORESULT
* on failure due to small n. Compare esl_gumbel. xref J12/93.
* SRE, Wed Nov 27 11:17:59 2013
*/
#include "esl_config.h"
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "easel.h"
#include "esl_exponential.h"
#include "esl_fileparser.h"
#include "esl_histogram.h"
#include "esl_minimizer.h"
#include "esl_random.h"
#include "esl_stats.h"
#include "esl_vectorops.h"
#include "esl_hyperexp.h"
/****************************************************************************
*# 1. The ESL_HYPEREXP object
****************************************************************************/
/* Function: esl_hyperexp_Create()
*
* Purpose: Creates an object to hold parameters for a <K>-component
* hyperexponential.
*
* Parameters in the object are initialized
* ($q_k = \frac{1}{K}$, $\lambda_k = 1$, $\mu = 0$), but
* the caller will want to set these according to its own
* purposes.
*
* Args: K - number of components in the mixture
*
* Returns: ptr to newly allocated/initialized <ESL_HYPEREXP> object.
*
* Throws: NULL on allocation failure.
*/
ESL_HYPEREXP *
esl_hyperexp_Create(int K)
{
int status;
ESL_HYPEREXP *h = NULL;
int k;
ESL_ALLOC(h, sizeof(ESL_HYPEREXP));
h->q = h->lambda = h->wrk = NULL;
h->fixlambda = NULL;
h->K = K;
h->fixmix = FALSE;
ESL_ALLOC(h->q, sizeof(double) * K);
ESL_ALLOC(h->lambda, sizeof(double) * K);
ESL_ALLOC(h->wrk, sizeof(double) * K);
ESL_ALLOC(h->fixlambda, sizeof(char) * K);
for (k = 0; k < K; k++)
{
h->q[k] = 1. / (double) K;
h->lambda[k] = 1.;
h->fixlambda[k]= 0;
}
h->mu = 0.;
return h;
ERROR:
esl_hyperexp_Destroy(h);
return NULL;
}
/* Function: esl_hyperexp_Destroy()
*
* Purpose: Deallocates the hyperexponential parameter object <h>.
*
* Args: h - ptr to the object to be deallocated.
*
* Returns: (void).
*/
void
esl_hyperexp_Destroy(ESL_HYPEREXP *h)
{
if (h == NULL) return;
if (h->q != NULL) free(h->q);
if (h->lambda != NULL) free(h->lambda);
if (h->wrk != NULL) free(h->wrk);
if (h->fixlambda!= NULL) free(h->fixlambda);
free(h);
}
/* Function: esl_hyperexp_Copy()
*
* Purpose: Makes a copy of the hyperexponential parameter object <src>
* in <dest>. Caller must have already allocated <dest> to have
* (at least) the same number of components as <src>.
*
* Args: src - object to be copied
* dest - allocated object to copy <src> into
*
* Returns: <eslOK> on success.
*
* Throws: <eslEINCOMPAT> if <dest> isn't allocated with enough
* components to hold a copy of <src>.
*/
int
esl_hyperexp_Copy(ESL_HYPEREXP *src, ESL_HYPEREXP *dest)
{
int k;
if (dest->K < src->K)
ESL_EXCEPTION(eslEINCOMPAT, "hyperexponential too small to copy into");
for (k = 0; k < src->K; k++)
{
dest->q[k] = src->q[k];
dest->lambda[k] = src->lambda[k];
dest->fixlambda[k]= src->fixlambda[k];
}
dest->mu = src->mu;
dest->K = src->K;
dest->fixmix = src->fixmix;
return eslOK;
}
/* Function: esl_hyperexp_FixedUniformMixture()
*
* Purpose: Set the mixture coeffients to a uniform (1/K) distribution,
* and fix them there so they aren't estimable parameters.
*/
int
esl_hyperexp_FixedUniformMixture(ESL_HYPEREXP *h)
{
int k;
for (k = 0; k < h->K; k++) h->q[k] = 1./(double)h->K;
h->fixmix = TRUE;
return eslOK;
}
/* Function: esl_hyperexp_SortComponents()
*
* Purpose: Rearrange the components in a hyperexponential in
* order of lambda values, with the highest lambda first.
*
* Stupid $O(K^2)$ selection sort algorithm here, because we
* expect $K$ to be small.
*/
int
esl_hyperexp_SortComponents(ESL_HYPEREXP *h)
{
int k, kp;
char ctmp;
double dtmp;
for (k = 0; k < h->K-1; k++)
{
kp = k + esl_vec_DArgMax(h->lambda+k, h->K-k);
if (k != kp)
{
dtmp = h->q[k]; h->q[k] = h->q[kp]; h->q[kp] = dtmp;
dtmp = h->lambda[k]; h->lambda[k] = h->lambda[kp]; h->lambda[kp] = dtmp;
ctmp = h->fixlambda[k]; h->fixlambda[k] = h->fixlambda[kp]; h->fixlambda[kp] = ctmp;
}
}
return eslOK;
}
/* Function: esl_hyperexp_Write()
*
* Purpose: Write hyperexponential parameters from <hxp> to an open <fp>.
*
* The output format is suitable for input by <esl_hyperexp_Read()>.
*
* Returns: <eslOK> on success.
*
* Throws: <eslEWRITE> on any write error.
*/
int
esl_hyperexp_Write(FILE *fp, ESL_HYPEREXP *hxp)
{
int k;
if (fprintf(fp, "%8d # number of components\n", hxp->K) < 0) ESL_EXCEPTION(eslEWRITE, "hyperexp write failed");
if (fprintf(fp, "%8.2f # mu (for all components)\n", hxp->mu) < 0) ESL_EXCEPTION(eslEWRITE, "hyperexp write failed");
for (k = 0; k < hxp->K; k++)
if (fprintf(fp, "%8.6f %12.6f # q[%d], lambda[%d]\n",
hxp->q[k], hxp->lambda[k], k, k) < 0) ESL_EXCEPTION(eslEWRITE, "hyperexp write failed");
return eslOK;
}
/* Function: esl_hyperexp_Dump()
*
* Purpose: Dump hyperexponential parameters from <hxp> to an open <fp>,
* all on one line with no comments.
*
* The output format is suitable for input by
* <esl_hyperexp_Read()>, like <esl_hyperexp_Write()>,
* though it's intended as a diagnostic dump of the
* contents of the object.
*
* Returns: <eslOK> on success.
*/
int
esl_hyperexp_Dump(FILE *fp, ESL_HYPEREXP *hxp)
{
int k;
fprintf(fp, "%2d ", hxp->K);
fprintf(fp, "%6.2f ", hxp->mu);
for (k = 0; k < hxp->K; k++)
fprintf(fp, "%5.3f %9.6f ", hxp->q[k], hxp->lambda[k]);
fprintf(fp, "\n");
return eslOK;
}
/*----------------- end ESL_HYPEREXP object maintenance --------------------*/
/****************************************************************************
* 2. Evaluating densities and distributions
****************************************************************************/
/* all lambda_k > 0
* all q_k are probabilities, \sum_k q_k = 1 [watch out for q_k=0 in log(q_k)].
* mu <= x < infinity [mu=x is not a problem]
*/
/* Function: esl_hxp_pdf()
*
* Purpose: Returns the probability density function $P(X=x)$ for
* quantile <x>, given hyperexponential parameters <h>.
*/
double
esl_hxp_pdf(double x, ESL_HYPEREXP *h)
{
double pdf = 0.;
int k;
if (x < h->mu) return 0.;
for (k = 0; k < h->K; k++)
pdf += h->q[k] * esl_exp_pdf(x, h->mu, h->lambda[k]);
return pdf;
}
/* Function: esl_hxp_logpdf()
*
* Purpose: Returns the log of the PDF ($\log P(X=x)$) for quantile <x>,
* given hyperexponential parameters <h>.
*/
double
esl_hxp_logpdf(double x, ESL_HYPEREXP *h)
{
int k;
double z;
if (x < h->mu) return -eslINFINITY;
for (k = 0; k < h->K; k++)
if (h->q[k] == 0.0)
h->wrk[k] = -eslINFINITY;
else
h->wrk[k] = log(h->q[k]) + esl_exp_logpdf(x, h->mu, h->lambda[k]);
z = esl_vec_DLogSum(h->wrk, h->K);
return z;
}
/* Function: esl_hxp_cdf()
*
* Purpose: Returns the cumulative distribution function $P(X \leq x)$
* for quantile <x>, given hyperexponential parameters <h>.
*/
double
esl_hxp_cdf(double x, ESL_HYPEREXP *h)
{
double cdf = 0.;
int k;
if (x < h->mu) return 0.;
for (k = 0; k < h->K; k++)
cdf += h->q[k] * esl_exp_cdf(x, h->mu, h->lambda[k]);
return cdf;
}
/* Function: esl_hxp_logcdf()
*
* Purpose: Returns the log of the CDF $\log P(X \leq x)$
* for quantile <x>, given hyperexponential parameters <h>.
*/
double
esl_hxp_logcdf(double x, ESL_HYPEREXP *h)
{
int k;
if (x < h->mu) return -eslINFINITY;
for (k = 0; k < h->K; k++)
if (h->q[k] == 0.0)
h->wrk[k] = -eslINFINITY;
else
h->wrk[k] = log(h->q[k]) + esl_exp_logcdf(x, h->mu, h->lambda[k]);
return esl_vec_DLogSum(h->wrk, h->K);
}
/* Function: esl_hxp_surv()
*
* Purpose: Returns the survivor function $P(X > x)$ (1-CDF)
* for quantile <x>, given hyperexponential parameters <h>.
*/
double
esl_hxp_surv(double x, ESL_HYPEREXP *h)
{
double srv = 0.;
int k;
if (x < h->mu) return 1.0;
for (k = 0; k < h->K; k++)
srv += h->q[k] * esl_exp_surv(x, h->mu, h->lambda[k]);
return srv;
}
/* Function: esl_hxp_logsurv()
*
* Purpose: Returns the log survivor function $\log P(X > x)$ (log(1-CDF))
* for quantile <x>, given hyperexponential parameters <h>.
*/
double
esl_hxp_logsurv(double x, ESL_HYPEREXP *h)
{
int k;
if (x < h->mu) return 0.0;
for (k = 0; k < h->K; k++)
if (h->q[k] == 0.0)
h->wrk[k] = -eslINFINITY;
else
h->wrk[k] = log(h->q[k]) + esl_exp_logsurv(x, h->mu, h->lambda[k]);
return esl_vec_DLogSum(h->wrk, h->K);
}
/* Function: esl_hxp_invcdf()
*
* Purpose: Calculates the inverse CDF for a hyperexponential <h>
* returning the quantile <x> at which the CDF is <p>.
*
* The inverse CDF of a mixture model has no
* analytical expression as far as I'm aware. The calculation
* here is a computationally expensive, brute force bisection
* search in <x> using the CDF function. It will suffice for
* a small number of calls (for plotting applications, for example),
* but it is not sufficient for a large number of calls.
*/
double
esl_hxp_invcdf(double p, ESL_HYPEREXP *h)
{
double x1, x2, xm; /* low, high guesses at x */
double f2, fm;
double tol = 1e-6;
x1 = h->mu;
x2 = h->mu + 1.;
do { /* bracket */
x2 = x2 + 2.*(x2-x1);
f2 = esl_hxp_cdf(x2, h);
} while (f2 < p);
do { /* bisection */
xm = (x1+x2) / 2.;
fm = esl_hxp_cdf(xm, h);
if (fm > p) x2 = xm;
else if (fm < p) x1 = xm;
else return xm; /* unlikely case of fm==cdf */
} while ( (x2-x1)/(x1+x2-2*h->mu) > tol);
xm = (x1+x2) / 2.;
return xm;
}
/*-------------------- end densities & distributions ------------------------*/
/****************************************************************************
* 3. Generic API routines: for general interface w/ histogram module
****************************************************************************/
/* Function: esl_hxp_generic_pdf()
*
* Purpose: Generic-API version of PDF call.
*/
double
esl_hxp_generic_pdf(double x, void *params)
{
ESL_HYPEREXP *h = (ESL_HYPEREXP *) params;
return esl_hxp_pdf(x, h);
}
/* Function: esl_hxp_generic_cdf()
*
* Purpose: Generic-API version of CDF call.
*/
double
esl_hxp_generic_cdf(double x, void *params)
{
ESL_HYPEREXP *h = (ESL_HYPEREXP *) params;
return esl_hxp_cdf(x, h);
}
/* Function: esl_hxp_generic_surv()
*
* Purpose: Generic-API version of survivor function.
*/
double
esl_hxp_generic_surv(double x, void *params)
{
ESL_HYPEREXP *h = (ESL_HYPEREXP *) params;
return esl_hxp_surv(x, h);
}
/* Function: esl_hxp_generic_invcdf()
*
* Purpose: Generic-API version of inverse CDF.
*/
double
esl_hxp_generic_invcdf(double p, void *params)
{
ESL_HYPEREXP *h = (ESL_HYPEREXP *) params;
return esl_hxp_invcdf(p, h);
}
/*------------------------ end generic API ---------------------------------*/
/****************************************************************************
* 4. Dumping plots for files
****************************************************************************/
/* Function: esl_hxp_Plot()
*
* Purpose: Plot some function <func> (for instance, <esl_hxp_pdf()>)
* for hyperexponential parameters <h>, for a range of
* quantiles x from <xmin> to <xmax> in steps of <xstep>;
* output to an open stream <fp> in xmgrace XY input format.
*
* Returns: <eslOK> on success.
*
* Throws: <eslEWRITE> on any system write error.
*/
int
esl_hxp_Plot(FILE *fp, ESL_HYPEREXP *h,
double (*func)(double x, ESL_HYPEREXP *h),
double xmin, double xmax, double xstep)
{
double x;
for (x = xmin; x <= xmax; x += xstep)
if (fprintf(fp, "%f\t%g\n", x, (*func)(x, h)) < 0) ESL_EXCEPTION_SYS(eslEWRITE, "hyperexp plot write failed");
if (fprintf(fp, "&\n") < 0) ESL_EXCEPTION_SYS(eslEWRITE, "hyperexp plot write failed");
return eslOK;
}
/*-------------------- end plot dumping routines ---------------------------*/
/****************************************************************************
* 5. Sampling
****************************************************************************/
/* Function: esl_hxp_Sample()
*
* Purpose: Sample a random variate x from a hyperexponential <h>,
* given random number source <r>.
*/
double
esl_hxp_Sample(ESL_RANDOMNESS *r, ESL_HYPEREXP *h)
{
int k;
k = esl_rnd_DChoose(r, h->q, h->K);
return esl_exp_Sample(r, h->mu, h->lambda[k]);
}
/*--------------------------- end sampling ---------------------------------*/
/****************************************************************************
* 6. File input (mixture models are a little too complex to set on commandline)
****************************************************************************/
/* Function: esl_hyperexp_Read()
*
* Purpose: Reads hyperexponential parameters from an open <e>.
* which is an <ESL_FILEPARSER> tokenizer for an open stream.
*
* The first token is <K>, the number of mixture components.
* The second token is <mu>, the x offset shared by all components.
* Then for each mixture component <k=1..K>, it reads
* a mixture coefficient <q[k]> and a decay parameter
* <lambda[k]>.
*
* The <2K+2> data tokens must occur in this order, but
* they can be grouped into any number of lines, because the
* parser ignores line breaks.
*
* Anything after a <\#> character on a line is a comment, and
* is ignored.
*
* Returns: <eslOK> on success, and <ret_hxp> points to a new <ESL_HYPEREXP>
* object.
* <eslEFORMAT> on "normal" parse failure caused by a bad file
* format that's likely the user's fault.
*
* Throws: <eslEMEM> if allocation of the new <ESL_HYPEREXP> fails.
*
*
* FIXME: All our mixture models (esl_dirichlet, for example) should be
* reconciled w/ identical interfaces & behaviour.
*/
int
esl_hyperexp_Read(ESL_FILEPARSER *e, ESL_HYPEREXP **ret_hxp)
{
ESL_HYPEREXP *hxp = NULL;
char *tok;
int status = eslOK;
int nc;
int k;
double sum;
esl_fileparser_SetCommentChar(e, '#');
if ((status = esl_fileparser_GetToken(e, &tok, NULL)) != eslOK) goto ERROR;
nc = atoi(tok);
if (nc < 1) {
sprintf(e->errbuf, "Expected # of components K >= 1 as first token");
goto ERROR;
}
if ((hxp = esl_hyperexp_Create(nc)) == NULL) return eslEMEM; /* percolation */
if ((status = esl_fileparser_GetToken(e, &tok, NULL)) != eslOK) goto ERROR;
hxp->mu = atof(tok);
for (k = 0; k < hxp->K; k++)
{
if ((status = esl_fileparser_GetToken(e, &tok, NULL)) != eslOK) goto ERROR;
hxp->q[k] = atof(tok);
if ((status = esl_fileparser_GetToken(e, &tok, NULL)) != eslOK) goto ERROR;
hxp->lambda[k] = atof(tok);
if (hxp->q[k] < 0. || hxp->q[k] > 1.) {
sprintf(e->errbuf, "Expected a mixture coefficient q[k], 0<=q[k]<=1");
goto ERROR;
}
if (hxp->lambda[k] <= 0.) {
sprintf(e->errbuf, "Expected a lambda parameter, lambda>0");
goto ERROR;
}
}
sum = esl_vec_DSum(hxp->q, hxp->K);
if (fabs(sum-1.0) > 0.05) {
sprintf(e->errbuf, "Expected mixture coefficients to sum to 1");
goto ERROR;
}
esl_vec_DNorm(hxp->q, hxp->K);
*ret_hxp = hxp;
return eslOK;
ERROR:
esl_hyperexp_Destroy(hxp);
return eslEFORMAT;
}
/* Function: esl_hyperexp_ReadFile()
*
* Purpose: Convenience wrapper around <esl_hyperexp_Read()> that takes
* a filename as an argument, instead of an open <ESL_FILEPARSER>.
*
* This lets you quickly read an object from a file, but it
* limits your ability to deal gracefully and flexibly with
* 'normal' errors like 'file not found' or 'bad file format'.
* Here, all errors are fatal.
*
* Returns: <eslOK> on success.
*
* Throws: <eslEMEM> on an allocation failure.
*
* <eslEFORMAT> on any parse error. Diagnostic information is
* unavailable, because the <ESL_FILEPARSER> that's holding
* that information is internal to this function.
*
* <eslENOTFOUND> on any failure to open the file.
*/
int
esl_hyperexp_ReadFile(char *filename, ESL_HYPEREXP **ret_hxp)
{
FILE *fp;
ESL_FILEPARSER *e;
int status;
if ((fp = fopen(filename, "r")) == NULL)
ESL_EXCEPTION(eslENOTFOUND, "file not found");
if ((e = esl_fileparser_Create(fp)) == NULL) {
fclose(fp);
ESL_EXCEPTION(eslEMEM, "failed to create fileparser");
}
esl_fileparser_SetCommentChar(e, '#');
status = esl_hyperexp_Read(e, ret_hxp);
esl_fileparser_Destroy(e);
fclose(fp);
return status;
}
/****************************************************************************
* 7. ML fitting to complete data
****************************************************************************/
/* This structure is used to sneak the data into minimizer's generic
* (void *) API for all aux data
*/
struct hyperexp_data {
double *x;
int n;
ESL_HYPEREXP *h;
};
/* Given hyperexponential parameters in <h>;
* do appropriate c.o.v.'s to unconstrained real parameters
* and fill in the packed parameter vector <p>.
*
* <p> must be allocated for at least (2K-1) doubles: K-1 mixture
* coefficients and K lambda parameters. (mu is not a free param).
*
* First K-1 are $Q_1..Q_{K-1}$ mixture coefficient parameters; $Q_0$ implicitly 0;
* cov is $q_k = \frac{e^{Q_k}}{\sum_j e^{Q_j}}$; $Q_k = \log(q_k) - \log(q_0)$.
* Then K lambda params;
* lambda cov is $\lambda = e^w$, $w = \log(\lambda)$.
*/
static void
hyperexp_pack_paramvector(double *p, int np, ESL_HYPEREXP *h)
{
int i; /* counter in parameter vector p */
int k; /* counter in mixture components */
double z; /* tmp variable */
/* mixture coefficients */
i = 0;
if (! h->fixmix) {
z = log(h->q[0]);
for (k = 1; k < h->K; k++)
p[i++] = log(h->q[k]) - z;
}
/* exponential parameters */
for (k = 0; k < h->K; k++)
if (! h->fixlambda[k])
p[i++] = log(h->lambda[k]);
}
/* Same as above but in reverse: given parameter vector <p>,
* <np> = 2K-1, do appropriate c.o.v. back to desired parameter space, and
* update the hyperexponential <h>.
*/
static void
hyperexp_unpack_paramvector(double *p, int np, ESL_HYPEREXP *h)
{
int i; /* counter in parameter vector p */
int k; /* counter in mixture components */
double z; /* tmp variable */
/* Fetch the params in their c.o.v. space first
*/
i = 0;
if (! h->fixmix) {
h->q[0] = 0; /* implicitly */
for (k = 1; k < h->K; k++)
h->q[k] = p[i++];
}
for (k = 0; k < h->K; k++)
if (! h->fixlambda[k])
h->lambda[k] = p[i++];
/* Convert mix coefficients back to probabilities;
* their c.o.v. is q_k = e^{Q_k} / \sum_k e^{Q_k}
* which rearranges to exp(Q_k - log[\sum_k e^Q_k]),
* and we have the DLogSum() function to compute the log sum.
*/
if (! h->fixmix) {
z = esl_vec_DLogSum(h->q, h->K);
for (k = 0; k < h->K; k++)
h->q[k] = exp(h->q[k] - z);
}
/* lambda c.o.v. is \lambda = e^w */
for (k = 0; k < h->K; k++)
if (! h->fixlambda[k])
h->lambda[k] = exp(h->lambda[k]);
}
/* The log likelihood function to be optimized by ML fitting:
* This needs to be careful of a case where a lambda = inf.
*/
static double
hyperexp_complete_func(double *p, int np, void *dptr)
{
struct hyperexp_data *data = (struct hyperexp_data *) dptr;
ESL_HYPEREXP *h = data->h;
double logL = 0.;
int i;
hyperexp_unpack_paramvector(p, np, h);
for (i = 0; i < data->n; i++)
logL += esl_hxp_logpdf(data->x[i], h);
return -logL;
}
/* The gradient of the NLL w.r.t. each free parameter in p.
*/
static void
hyperexp_complete_gradient(double *p, int np, void *dptr, double *dp)
{
struct hyperexp_data *data = (struct hyperexp_data *) dptr;
ESL_HYPEREXP *h = data->h;
double pdf;
int i,k;
int pidx;
hyperexp_unpack_paramvector(p, np, h);
esl_vec_DSet(dp, np, 0.);
for (i = 0; i < data->n; i++)
{
/* FIXME: I think the calculation below may need to be done
* in log space, to avoid underflow errors; see complete_binned_gradient()
*/
/* Precalculate q_k PDF_k(x) terms, and their sum */
for (k = 0; k < h->K; k++)
h->wrk[k] = h->q[k] * esl_exp_pdf(data->x[i], h->mu, h->lambda[k]);
pdf = esl_vec_DSum(h->wrk, h->K);
pidx = 0;
if (! h->fixmix) {
for (k = 1; k < h->K; k++) /* generic d/dQ solution for mixture models */
dp[pidx++] -= h->wrk[k]/pdf - h->q[k];
}
for (k = 0; k < h->K; k++)
if (! h->fixlambda[k])
dp[pidx++] -= (1.-h->lambda[k]*(data->x[i]-h->mu))*h->wrk[k]/pdf; /* d/dw */
}
}
/* Function: esl_hxp_FitGuess()
*
* Purpose: Given a sorted vector of <n> observed data samples <x[]>,
* from smallest <x[0]> to largest <x[n-1]>, calculate a
* very crude guesstimate of a fit -- suitable only as a starting
* point for further optimization -- and return those parameters
* in <h>.
*
* Assigns $q_k \propto \frac{1}{k}$ and $\mu = \min_i x_i$;
* splits $x$ into $K$ roughly equal-sized bins, and
* and assigns $\lambda_k$ as the ML estimate from bin $k$.
* (If $q_k$ coefficients have already been fixed to
* known values, this step is skipped.)
*/
int
esl_hxp_FitGuess(double *x, int n, ESL_HYPEREXP *h)
{
double tmu; /* current mu */
double mean; /* mean (x-tmu) in a bin */
int i,k;
int imin, imax;
h->mu = x[0]; /* minimum */
for (k = 0; k < h->K; k++)
{
if (! h->fixmix)
h->q[k] = 1 / (double)(k+1); /* priors ~ 1, 1/2, 1/3... */
imin = (int) ((double)(k*n)/(double)h->K);
imax = (int) ((double)((k+1)*n)/(double)h->K);
tmu = x[imin];
mean = 0.;
for (i = imin; i < imax; i++)
mean += x[i] - tmu;
mean /= (double)(imax-imin);
h->lambda[k] = 1 / mean;
}
esl_vec_DNorm(h->q, h->K);
return eslOK;
}
/* Function: esl_hxp_FitComplete()
*
* Purpose: Given a vector of <n> observed data samples <x[]>
* (sorted or unsorted), and an initial guess <h> for
* a hyperexponential, find maximum likelihood parameters
* by conjugate gradient descent optimization, starting
* from <h> and leaving the final optimized solution in
* <h>.
*
* Returns: <eslOK> on success, and <h> contains the fitted
* hyperexponential parameters.
*
* Throws: <eslEMEM> on allocation error, and <h> is left in
* in its initial state.
*/
int
esl_hxp_FitComplete(double *x, int n, ESL_HYPEREXP *h)
{
struct hyperexp_data data;
double *p = NULL;
int np;
double fx;
int i;
int status;
/* Determine number of free parameters and allocate */
np = 0;
if (! h->fixmix) np += h->K-1; /* K-1 mix coefficients... */
for (i = 0; i < h->K; i++) /* ...and up to K lambdas free */
if (! h->fixlambda[i]) np++;
ESL_ALLOC(p, sizeof(double) * np);
/* Copy shared info into the "data" structure */
data.x = x;
data.n = n;
data.h = h;
/* From h, create the parameter vector. */
hyperexp_pack_paramvector(p, np, h);
/* Feed it all to the mighty optimizer. */
status = esl_min_ConjugateGradientDescent(NULL, p, np,
&hyperexp_complete_func,
&hyperexp_complete_gradient,
(void *) (&data), &fx, NULL);
if (status != eslOK) goto ERROR;
/* Convert the final parameter vector back to a hyperexponential
*/
hyperexp_unpack_paramvector(p, np, h);
free(p);
esl_hyperexp_SortComponents(h);
return eslOK;
ERROR:
free(p);
return status;
}
/****************************************************************************
* 8. Maximum likelihood fitting, complete binned data xref STL9/143-144
****************************************************************************/
/* minimizer API only allows us one generic void ptr to pass
* our data through:
*/
struct hyperexp_binned_data {
ESL_HISTOGRAM *g;
ESL_HYPEREXP *h;
};
static double
hyperexp_complete_binned_func(double *p, int np, void *dptr)
{
struct hyperexp_binned_data *data = (struct hyperexp_binned_data *) dptr;
ESL_HISTOGRAM *g = data->g;
ESL_HYPEREXP *h = data->h;
double logL = 0.;
double ai, delta;
int i,k;
hyperexp_unpack_paramvector(p, np, h);
delta = g->w;
/* counting over occupied, uncensored histogram bins */
for (i = g->cmin; i <= g->imax; i++)
{
if (g->obs[i] == 0) continue; /* skip unoccupied ones */
ai = esl_histogram_Bin2LBound(g, i);
if (ai < h->mu) ai = h->mu; /* careful about the left boundary: no x < h->mu */
for (k = 0; k < h->K; k++)
{
h->wrk[k] = log(h->q[k]) - h->lambda[k]*(ai-h->mu);
if (delta * h->lambda[k] < eslSMALLX1)
h->wrk[k] += log(delta * h->lambda[k]);
else
h->wrk[k] += log(1 - exp(-delta * h->lambda[k]));
}
logL += g->obs[i] * esl_vec_DLogSum(h->wrk, h->K);
}
return -logL;
}
static void
hyperexp_complete_binned_gradient(double *p, int np, void *dptr, double *dp)
{
struct hyperexp_binned_data *data = (struct hyperexp_binned_data *) dptr;
ESL_HISTOGRAM *g = data->g;
ESL_HYPEREXP *h = data->h;
int i,k;
int pidx;
double z;
double tmp;
double ai, delta;
hyperexp_unpack_paramvector(p, np, h);
esl_vec_DSet(dp, np, 0.);
delta = g->w;
/* counting over occupied, uncensored histogram bins */
for (i = g->cmin; i <= g->imax; i++)
{
if (g->obs[i] == 0) continue;
ai = esl_histogram_Bin2LBound(g, i);
if (ai < h->mu) ai = h->mu; /* careful about the left boundary: no x < h->mu */
/* Calculate log (q_m alpha_m(a_i) terms
*/
for (k = 0; k < h->K; k++)
{
h->wrk[k] = log(h->q[k]) - h->lambda[k]*(ai-h->mu);
if (delta * h->lambda[k] < eslSMALLX1)
h->wrk[k] += log(delta * h->lambda[k]);
else
h->wrk[k] += log(1 - exp(-delta * h->lambda[k]));
}
z = esl_vec_DLogSum(h->wrk, h->K); /* z= log \sum_k q_k alpha_k(a_i) */
/* Bump the gradients for Q_1..Q_{K-1} */
pidx = 0;
if (! h->fixmix) {
for (k = 1; k < h->K; k++)
dp[pidx++] -= g->obs[i] * (exp(h->wrk[k] - z) - h->q[k]);
}
/* Bump the gradients for w_0..w_{K-1}
*/
for (k = 0; k < h->K; k++)
if (! h->fixlambda[k])
{
tmp = log(h->q[k]) + log(h->lambda[k])- h->lambda[k]*(ai-h->mu);
tmp = exp(tmp - z);
tmp *= (ai + delta - h->mu) * exp(-delta * h->lambda[k]) - (ai - h->mu);
dp[pidx++] -= g->obs[i] * tmp;
}
}
}