Custom IGChartView Labelling (Objective - C / Xamarin.iOS)

@interface MyCustomChartDelegate : NSObject
@end
  -(NSString *)chartView:(IGChartView *)chartView labelForAxis:(IGAxis *)axis withItem:(NSObject *)item
{
  // We need to filter out that we are looking at the Y-axis. I know in this case that my Y axis has
  // a key value of "y".
  if([axis.key isEqualToString:@"y"])
  {
    NSNumber* num = ((NSNumber*) item);
    NSNumberFormatter* formatter = [[NSNumberFormatter alloc]init];
    NSString* longString = [formatter stringFromNumber:num];

    // I want to make any number > 1000 into a "k" denomination, so if the string is 4 or more characters then clip it, add a k and return.

    if (longString.length > 3)
    {
      NSString* subString = [longString substringToIndex:(longString.length-3)];
      subString = [NSString stringWithFormat:@"%@%@",subString,@"K"];
      return subString;
    }

    return longString;
  }

  // Since we are overriding this method we also need to handle the X - axis labels. Since
  // IGLineSeries is a CategorySeries and the x - axis is the category axis in this case, we can
  // cast the item to a IGDataPoint and return the label.
  //IGDataPoint* pt = (IGDataPoint*)item;
  //return pt.label;

  // But just doing that isn't any fun. So instead lets get the underlying data object and make a better label.

  IGDataPoint* pt = (IGDataPoint*)item;

  IGColumnSeries* colSeries = (IGColumnSeries*)chartView.series[0];

  MyDataClass* dataObj = (MyDataClass*)[colSeries.dataSource objectForDataPoint:pt inSeries:colSeries];
  NSString* firstInitial = [dataObj.firstName substringToIndex:1];

  return [NSString stringWithFormat:@"%@. %@", firstInitial, dataObj.lastName];
}