ContentView_6.swift

private func change(location: CGPoint) {
        // creating vector from location point
        let vector = CGVector(dx: location.x, dy: location.y)
        
        // geting angle in radian need to subtract the knob radius and padding 
        let angle = atan2(vector.dy - (config.knobRadius + 10), vector.dx - (config.knobRadius + 10)) + .pi/2.0
        
        // convert angle range from (-pi to pi) to (0 to 2pi)
        let fixedAngle = angle < 0.0 ? angle + 2.0 * .pi : angle
        // convert angle value to temperature value
        let value = fixedAngle / (2.0 * .pi) * config.totalValue
        
        if value >= config.minimumValue && value <= config.maximumValue {
            temperatureValue = value
            angleValue = fixedAngle * 180 / .pi // converting to degree
        }
    }