User`s guide

Fully Inlined S-Function with the mdlRTW Routine

4-27

matlabroot/simulink/src/sfun_directlook.c

* File : sfun_directlook.c

* Abstract:

* Direct 1-D lookup. Here we are trying to compute an approximate

* solution, p(x) to an unknown function f(x) at x=x0, given data point

* pairs (x,y) in the form of a x data vector and a y data vector. For a

* given data pair (say the i’th pair), we have y_i = f(x_i). It is

* assumed that the x data values are monotonically increasing. If the

* x0 is outside of the range of the x data vector, then the first or

* last point will be returned.

* This function returns the “nearest” y0 point for a given x0. No

* interpolation is performed.

* The S-function parameters are:

* XData - double vector

* YData - double vector

* XDataEvenlySpacing - double scalar 0 (false) or 1 (true)

* The third parameter cannot be changed during simulation.

* To build:

* mex sfun_directlook.c lookup_index.c

* $Revision: 1.3 $

#define S_FUNCTION_NAME sfun_directlook

#define S_FUNCTION_LEVEL 2

#include <math.h>

#include “simstruc.h”

#include <float.h>

/*=========*

* Defines *

*=========*/

#define XVECT_PIDX 0

#define YVECT_PIDX 1

#define XDATAEVENLYSPACED_PIDX 2

#define NUM_PARAMS 3

#define XVECT(S) ssGetSFcnParam(S,XVECT_PIDX)

#define YVECT(S) ssGetSFcnParam(S,YVECT_PIDX)

#define XDATAEVENLYSPACED(S) ssGetSFcnParam(S,XDATAEVENLYSPACED_PIDX)