Fix: problem with smoothing if data points were at the same x position.
Fix: problem with smoothing if data points were at the same x position.

zuojx1013/ios-linechart,mruegenberg/ios-linechart,iosyoujian/ios-linechart,0x0c/ios-linechart,echo2046/ios-linechart,claudiuvintila/ios-linechart