//exit('{status:"error",value:'.json_encode($xvalues).',xmin:'.$xmin.',xmax:'.$xmax.',dx:'.$dx.',n:'.$n.'}');
$expr_str = decode($_REQUEST["expression"]);
if ($expr_str == 'spline') {
if (!isset($_REQUEST["points"])) {
exit('{status:"error",value:"Points not given for spline"}');
}
$points = json_decode($_REQUEST["points"]);
$do_fit = false;
if (isset($_REQUEST["fit"])) {
$do_fit = $_REQUEST["fit"];
}
if (sizeof($points) == 0) {
exit('{status:"error",value:"Empty points array given for spline"}');
}
$spline = new Spline();
$spline->add_points($points);
//exit('{status:"error",value:'.json_encode($points).'}');
if ($do_fit) {
$spline->fit_derivs();
} else {
$spline->fit();
}
$x_first = $spline->points[0]->x;
$x_last = $spline->points[sizeof($spline->points) - 1]->x;
$x_arr = array();
$m = sizeof($xvalues);
$empty = true;
for ($i = 0; $i < $m; $i += 1) {
$x = $xvalues[$i];
if ($x >= $x_first && $x <= $x_last) {
if ($empty && $x > $x_first) {
