Question

I’m trying to basically reverse this algorithm so that I get the time for a given y-Axis.

+ (CGFloat)yAxisForTime:(CGFloat)time
{
    CGFloat newTime = (float)(time * ((60 / [DataClass sharedInstance].timeInterval) / 2 ));
    return kTopBuffer + (44.0f * newTime);
}

+ (CGFloat)timeForYAxis:(CGFloat)y
{
    CGFloat newTime = (float)(y / ((60 * [DataClass sharedInstance].timeInterval) * 2 ));
    return kTopBuffer + (44.0f / newTime);
}

I have a brain fart today and can’t seem to get it right. How would I get the time for yAxis? I have yAxisForTime working good, but now just need to get timeForYAxis.

Answer 1

If

y = kTopBuffer + (44 * newtime)

Then

newTime = (y - kTopBuffer) / 44

and therefore

time = (newTime / ((60 / [DataClass sharedInstance].timeInterval) / 2 ))

So:

time = ( ((y - kTopBuffer) / 44) / ((60 / [DataClass sharedInstance].timeInterval) / 2 ))