main()
{
int ixin,ixout;
float ydin[NXIN][4],xout[NXOUT],yout[NXOUT],x;
for (ixout=0,x=fxout; ixout<NXOUT; ixout++,x+=dxout)
xout[ixout] = x;
csplin(NXIN,xin,yin,ydin);
intcub(0,NXIN,xin,ydin,NXOUT,xout,yout);
/* fwrite(yout,sizeof(float),NXOUT,stdout); */
pp1d(stdout,"Cubic spline",NXOUT,0,yout);
cmonot(NXIN,xin,yin,ydin);
intcub(0,NXIN,xin,ydin,NXOUT,xout,yout);
/* fwrite(yout,sizeof(float),NXOUT,stdout); */
pp1d(stdout,"Fritsch-Carlson method",NXOUT,0,yout);
cakima(NXIN,xin,yin,ydin);
intcub(0,NXIN,xin,ydin,NXOUT,xout,yout);
/* fwrite(yout,sizeof(float),NXOUT,stdout); */
pp1d(stdout,"Akima's method",NXOUT,0,yout);
}
Var* cubic_interp(Var* v0, Var* v1, Var* v2, char* type, float ignore)
{
float **yd, *out, *xp, *yp, *arena;
size_t npts, nout;
size_t i, j;
float x0, x1, x, h;
int done;
size_t count = 0;
int error = 0;
npts = V_DSIZE(v0);
nout = V_DSIZE(v2);
/* this is the hard way */
yd = calloc(npts, sizeof(float*));
xp = calloc(npts, sizeof(float));
yp = calloc(npts, sizeof(float));
arena = calloc(npts * 4, sizeof(float));
out = calloc(nout, sizeof(float));
for (i = 0; i < npts; i++) {
xp[count] = extract_float(v1, i);
yp[count] = extract_float(v0, i);
yd[count] = arena + 4 * count;
/* Handle deleted points and non-increasing data */
if (xp[count] == ignore || yp[count] == ignore) {
continue;
}
if (count && xp[count] <= xp[count - 1]) {
parse_error("Error: data is not monotonically increasing x1[%ld] = %f", i, xp[count]);
error = 1;
break;
}
count++;
}
/* this is the case if we're not monotonic increasing */
if (error) {
free(arena);
free(yd);
free(xp);
free(yp);
return (NULL);
}
npts = count;
cakima(npts, xp, yp, yd);
done = i = j = 0;
while (!done) {
if (i >= nout)
break;
else if (j >= npts)
break;
x0 = xp[j];
x1 = xp[j + 1];
x = extract_float(v2, i);
if (x == ignore) {
out[i] = ignore;
i++;
}
if (x < x0)
i++;
else if (x > x1)
j++;
else {
h = x - x0;
out[i] = yd[j][0] + h * (yd[j][1] + h * (yd[j][2] / 2.0 + h * yd[j][3] / 6.0));
i++;
}
}
free(arena);
free(yd);
free(xp);
free(yp);
return (newVal(V_ORG(v2), V_SIZE(v2)[0], V_SIZE(v2)[1], V_SIZE(v2)[2], DV_FLOAT, out));
}
