Читать книгу The Big R-Book - Philippe J. S. De Brouwer - Страница 272

median

While the mean (and the average in particular) is widely used, it is actually quite vulnerable to outliers. It would therefore, make sense to have a measure that is less influenced by the outliers and rather answers the question: what would a typical observation look like. The median is such measure.

central tendency – median

The median is the middle-value so that 50% of the observations are lower and 50% are higher.

x <- c(1:5,5e10,NA) x ## [1] 1e+00 2e+00 3e+00 4e+00 5e+00 5e+10 NA median(x) # no meaningful result with NAs ## [1] NA median(x,na.rm = TRUE) # ignore the NA ## [1] 3.5 # Note how the median is not impacted by the outlier, # but the outlier dominates the mean: mean(x, na.rm = TRUE) ## [1] 8333333336