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/*
* linear - perform a simple two point 2D linear interpolation
*
* given:
* x0, y0 first known point on the line
* x1, y1 second knonw 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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