question: public void updateCrosshairX ( double candidateX , int domainAxisIndex ) { double d = Math . abs ( candidateX - this . anchorX ) ; if ( d < this . distance ) { this . crosshairX = candidateX ; this . domainAxisIndex = domainAxisIndex ; this . distance = d ; } }
target:  Evaluates an x-value and if it is the closest to the anchor x-value it becomes the new crosshair value. <P> Used in cases where only the x-axis is numerical.