drawRect Method for GraphView

gistfile1.m

//Draws a Cartesian Coordinate system and graphs an equation on it. 
//Equation comes from GraphViewController (data source)
- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    CGPoint midPoint; //center in coordinate system
    midPoint.x = self.bounds.origin.x + self.bounds.size.width/2;
    midPoint.y = self.bounds.origin.y + self.bounds.size.height/2;
    
    //Draw Axes
    CGRect rect1 = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height);
    [AxesDrawer drawAxesInRect:rect1 originAtPoint:midPoint scale:[self scale]];
    
    
	UIGraphicsPushContext(context);
        
    //Set Drawing Options
    CGContextSetLineWidth(context, 2);
    [[UIColor redColor] setStroke];
    
    
    //Draw Graph
    
    BOOL haveMovedToPoint = NO; 
    
    for (CGFloat pixel = 0; pixel < midPoint.x*2; pixel++) { //Iterate over each pixel left to right, iOS coordinat system
        
        //Change frame of reference to Cartesian coordinate system
        
        
        CGFloat xPixelsFromCartesianOrigin = pixel-midPoint.x; //Distance from center to edge of screen
        xValue = xPixelsFromCartesianOrigin / [self scale];     //xValue in Units
        
        CGFloat yChange = [self.dataSource deltaY:self];  //Delegate calculates y-Value in units given x-Value in units
        CGFloat yPixelsFromCartesianOrigin = yChange * [self scale]; 

        //If this is the first iteration through the loop, move to point to begin drawing.
        if (haveMovedToPoint == NO)
        {
            CGContextMoveToPoint(context, 0, (self.bounds.size.height/2)-yPixelsFromCartesianOrigin);
            haveMovedToPoint = YES;
        }
        CGContextAddLineToPoint(context, pixel, (self.bounds.size.height/2)-yPixelsFromCartesianOrigin);
    }
    
    CGContextStrokePath(context);
	UIGraphicsPopContext();
}