목적 : 비교 대상 간에 값의 분포가 차이가 없는지 있는지 비교할 때 쓰임
a graphical method for comparing two probability distributions by plotting their quantiles against each other.
First, the set of intervals for the quantiles is chosen. A point (x, y) on the plot corresponds to one of the quantiles of the second distribution (y-coordinate) plotted against the same quantile of the first distribution (x-coordinate). Thus the line is a parametric curve with the parameter which is the (number of the) interval for the quantile.
If the two distributions being compared are similar, the points in the Q–Q plot will approximately lie on the line y = x. If the distributions are linearly related, the points in the Q–Q plot will approximately lie on a line, but not necessarily on the line y = x
qqnorm(x)으로
qqline(x, col=2)은 기본적으로 quantile 0.25와 0.75를 잇는 선을 그음
Geometric mean(geometry mean)
install.packages('psych')
geometric.mean(x,na.rm=TRUE)
up deg와 down deg 각자의 geometric mean을 구한 후에 빼준 후
qqnorm()과 qqplot으로 그림을 그려서 outlier를 찾으면 됨.