SPPlotView.m

  [[UIColor colorWithRed:0 green:192/255.0 blue:255/255.0 alpha:1] set];

  CGContextSetLineWidth(context, 1);
  CGContextSetLineJoin(context, kCGLineJoinRound);

  const CGFloat amplitude = halfHeight / 4;
  for(CGFloat x = 0; x < width; x += 0.5)
  {
    CGFloat y = amplitude * sinf(2 * M_PI * (x / width) * frequency) + halfHeight;

    if(x == 0)
      CGContextMoveToPoint(context, x, y);
    else
      CGContextAddLineToPoint(context, x, y);
  }

  CGContextStrokePath(context);