116 lines
2.9 KiB
C++
116 lines
2.9 KiB
C++
//
|
|
// interpolater.cxx -- routines to handle linear interpolation from a table of
|
|
// x,y The table must be sorted by "x" in ascending order
|
|
//
|
|
// Written by Curtis Olson, started April 1998.
|
|
//
|
|
// Copyright (C) 1998 Curtis L. Olson - curt@me.umn.edu
|
|
//
|
|
// This program is free software; you can redistribute it and/or
|
|
// modify it under the terms of the GNU General Public License as
|
|
// published by the Free Software Foundation; either version 2 of the
|
|
// License, or (at your option) any later version.
|
|
//
|
|
// This program is distributed in the hope that it will be useful, but
|
|
// WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU General Public License
|
|
// along with this program; if not, write to the Free Software
|
|
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
//
|
|
// $Id$
|
|
// (Log is kept at end of this file)
|
|
|
|
|
|
#include <string.h>
|
|
|
|
#include <Debug/fg_debug.h>
|
|
#include <zlib/zlib.h>
|
|
|
|
#include "interpolater.hxx"
|
|
|
|
|
|
// Constructor -- loads the interpolation table from the specified
|
|
// file
|
|
fgINTERPTABLE::fgINTERPTABLE( char *file ) {
|
|
char gzfile[256], line[256];
|
|
gzFile fd;
|
|
|
|
fgPrintf( FG_MATH, FG_INFO, "Initializing Interpolator for %s\n", file);
|
|
|
|
// First try "file.gz"
|
|
strcpy(gzfile, file);
|
|
strcat(gzfile, ".gz");
|
|
if ( (fd = gzopen(gzfile, "r")) == NULL ) {
|
|
// Next try "path"
|
|
if ( (fd = gzopen(file, "r")) == NULL ) {
|
|
fgPrintf(FG_MATH, FG_ALERT, "Cannot open file: %s\n", file);
|
|
}
|
|
}
|
|
|
|
size = 0;
|
|
while ( gzgets(fd, line, 250) != NULL ) {
|
|
if ( size < MAX_TABLE_SIZE ) {
|
|
sscanf(line, "%lf %lf\n", &(table[size][0]), &(table[size][1]));
|
|
size++;
|
|
} else {
|
|
fgPrintf( FG_MATH, FG_ALERT,
|
|
"fgInterpolateInit(): Exceed max table size = %d\n",
|
|
MAX_TABLE_SIZE );
|
|
}
|
|
}
|
|
|
|
gzclose(fd);
|
|
}
|
|
|
|
|
|
// Given an x value, linearly interpolate the y value from the table
|
|
double fgINTERPTABLE::interpolate(double x) {
|
|
int i;
|
|
double y;
|
|
|
|
i = 0;
|
|
|
|
while ( (x > table[i][0]) && (i < size) ) {
|
|
i++;
|
|
}
|
|
|
|
printf ("i = %d ", i);
|
|
|
|
if ( (i == 0) && (x < table[0][0]) ) {
|
|
fgPrintf( FG_MATH, FG_ALERT,
|
|
"fgInterpolateInit(): lookup error, x to small = %.2f\n", x);
|
|
return(0.0);
|
|
}
|
|
|
|
if ( x > table[i][0] ) {
|
|
fgPrintf( FG_MATH, FG_ALERT,
|
|
"fgInterpolateInit(): lookup error, x to big = %.2f\n", x);
|
|
return(0.0);
|
|
}
|
|
|
|
// y = y1 + (y0 - y1)(x - x1) / (x0 - x1)
|
|
y = table[i][1] +
|
|
( (table[i-1][1] - table[i][1]) *
|
|
(x - table[i][0]) ) /
|
|
(table[i-1][0] - table[i][0]);
|
|
|
|
return(y);
|
|
}
|
|
|
|
|
|
// Destructor
|
|
fgINTERPTABLE::~fgINTERPTABLE( void ) {
|
|
}
|
|
|
|
|
|
// $Log$
|
|
// Revision 1.1 1998/04/21 19:14:23 curt
|
|
// Modified Files:
|
|
// Makefile.am Makefile.in
|
|
// Added Files:
|
|
// interpolater.cxx interpolater.hxx
|
|
//
|
|
//
|