Sine Wave with fill using UIBezierPath

ViewController.swift

// Draw a sine curve with a fill

let centerY = frame.height / 2  // find the vertical center
let steps = 200                 // Divide the curve into steps
let stepX = frame.width / CGFloat(steps) // find the horizontal step distance

// Make a path
let path = UIBezierPath()
// Start in the lower left corner
path.moveToPoint(CGPoint(x: 0, y: frame.height))
// Draw a line up to the vertical center
path.addLineToPoint(CGPoint(x: 0, y: centerY))
// Loop and draw steps in straingt line segments
for i in 0...steps {
    let x = CGFloat(i) * stepX
    let y = (sin(Double(i) * 0.1) * 40) + Double(centerY)
    path.addLineToPoint(CGPoint(x: x, y: CGFloat(y)))
}
// Draw down to the lower right
path.addLineToPoint(CGPoint(x: frame.width, y: frame.height))
// Close the path
path.closePath()
// Render the path
let fillColor = UIColor.redColor()
fillColor.setFill()
path.fill()
// let strokeColor = UIColor.redColor()
// strokeColor.setStroke()
// path.lineWidth = 3
// path.stroke()