A simple test for outliers. This functions returns all extreme values (if any) found in the specified vector.
rp.outlier(x)vector of outlier values
Credit goes to PaulHurleyuk: https://stackoverflow.com/a/1444548/564164
Lund, R. E. 1975, "Tables for An Approximate Test for Outliers in Linear Models", Technometrics, vol. 17, no. 4, pp. 473-476.
Prescott, P. 1975, "An Approximate Test for Outliers in Linear Models", Technometrics, vol. 17, no. 1, pp. 129-132.