line chart: data points do not line up with x-axis tick marks

[dam13n]

everything seems to be offset backwards by 1 tick

[dam13n]

By changing the chart margin, I was able to fix this, but I'm not sure it'll cleanly work across different iPhones.

[dam13n]

Think I spoke too soon, haha. Just reduced the plot to two points. Way off. Looks like this now:

[dam13n]

Here's the issue I think. In the function - (void)setXLabels:(NSArray *)xLabels withWidth:(CGFloat)width, there is this code:

            NSInteger x = (index *  _xLabelWidth + _chartMarginLeft + _xLabelWidth /2.0 );
            NSInteger y = _chartMarginBottom + _chartCavanHeight;

            PNChartLabel *label = [[PNChartLabel alloc] initWithFrame:CGRectMake(x, y, (NSInteger)_xLabelWidth, (NSInteger)_chartMarginBottom)];
            [label setTextAlignment:NSTextAlignmentCenter];

Because the text alignment is set to center, there is no need to add the _xLabelWidth /2.0 to the x position (as that would be code that does centering itself).

Found another issue too. Gonna make a PR.