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/*
* linear - perform a simple two point 2D linear interpolation
*
* Copyright (C) 2005-2007,2021 Landon Curt Noll
*
* Calc is open software; you can redistribute it and/or modify it under
* the terms of the version 2.1 of the GNU Lesser General Public License
* as published by the Free Software Foundation.
*
* Calc 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 Lesser General
* Public License for more details.
*
* A copy of version 2.1 of the GNU Lesser General Public License is
* distributed with calc under the filename COPYING-LGPL. You should have
* received a copy with calc; if not, write to Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* Under source code control: 2005/12/12 06:41:50
* File existed as early as: 2005
*
* chongo <was here> /\oo/\ http://www.isthe.com/chongo/
* Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
*/
/*
* linear - perform a simple two point 2D linear interpolation
*
* given:
* x0, y0 first known point on the line
* x1, y1 second known point on the line
* x a given point to interpolate on
*
* returns:
* y such that (x,y) is on the line defined by (x0,y0) and (x1,y1)
*
* NOTE: The line cannot be vertical. So x0 != y0.
*/
define linear(x0, y0, x1, y1, x)
{
/* firewall */
if (!isnum(x0) || ! isnum(y0) || !isnum(x1) || ! isnum(y1) || !isnum(x)) {
quit "non-numeric argument passed to linear";
}
if (x0 == x1) {
quit "linear given a line with an infinite slope";
}
/* return y = y0 + (delta_Y/delta_X) * (x - x0) */
return y0 + (((y1-y0)/(x1-x0)) * (x - x0));
}
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