Theoretically in RF, inclusion of more points (more sampling rate) is thought to increment the gain of the regressor by declining the average distance between the predictions and the target, though, not only the training time continues its incremental trend, but also the aforesaid slope of the distance decelerates . In this regard, a comprehensive study was designed to find an optimized sampling rate in the range of {5,10,…,100}, according to both distance error and training time. The timing complexity reported in Figure 13 depicts the aforesaid evolution as the training size set increases, as expected. Besides, shown in Figure 14a, considering the average OF, the declining slope of the distance error decreases in defiance of sampling rate, until it reaches to 65%. Although the difference of the reported distances between the rates of 45% and 65% is less than 0.50 mm, to satisfy the condition of the OF, it was decided to use the sampling rate correlated with the global minimum distance (65%).