Stype.est 0.2.0

Performance improvements

• regstype() function optimized:
  • Replaced lm() with lm.fit() for initial fit
  • regweighteds() now called only once at end of loop instead of every iteration
  • Vectorized weight computation (removed inner for loops)
  • Replaced manual normal density formula with dnorm()
  • Simplified x/y input handling using as.matrix()