percoutl {dataprep}

Traditional percentile-based outlier removal

Description

The percentile-based outlier removal methods usually take a quantile as a threshold and values above it will be deleted. Here, two quantiles are used for both the top and the bottom. For the bottom, accordingly, values below the quantile threshold will be removed.

Usage

percoutl(data, start = NULL, end = NULL, group = NULL,
top = 0.995, bottom = 0.0025, by = "min", half = 30, cores = NULL)

Arguments

data

A data frame containing outliers (and missing values). Its columns from start to end will be checked.

start

The column number of the first selected variable.

end

The column number of the last selected variable.

group

The column number of the grouping variable. It can be selected according to whether the data needs to be processed in groups. If grouping is not required, leave it default (NULL); if grouping is required, set group as the column number (position) where the grouping variable is located. If there are more than one grouping variable, it can be turned into a longer group through combination and transformation in advance.

top

The top percentile is 0.995 by default.

bottom

The bottom percentile is 0.0025 by default.

by

The time extension unit by is a minute ("min") by default. The user can specify other time units. For example, "5 min" means that the time extension unit is 5 minutes.

half

Half window size of hourly moving average. It is 30 (minutes) by default, which is determined by the time expansion unit minute ("min").

cores

The number of CPU cores.

Details

Unlike condextr, a point-by-point considered outlier removal method, the traditional percentile-based percoutl is a "one size fits all" outlier deletion method. It may delete too many or too few values that are non-outliers or outliers respectively.

Value

A data frame after deleting outliers.

Author(s)

Chun-Sheng Liang <[e-mail]>

References

1. Example data is from https://smear.avaa.csc.fi/download. It includes particle number concentrations in SMEAR I Varrio forest.

2. Wickham, H., Francois, R., Henry, L. & Muller, K. 2017. dplyr: A Grammar of Data Manipulation. 0.7.4 ed. http://dplyr.tidyverse.org, https://github.com/tidyverse/dplyr.

3. Wickham, H., Francois, R., Henry, L. & Muller, K. 2019. dplyr: A Grammar of Data Manipulation. R package version 0.8.3. https://CRAN.R-project.org/package=dplyr.

4. Dowle, M., Srinivasan, A., Gorecki, J., Short, T., Lianoglou, S., Antonyan, E., 2017. data.table: Extension of 'data.frame', 1.10.4-3 ed, http://r-datatable.com.

5. Dowle, M., Srinivasan, A., 2021. data.table: Extension of 'data.frame'. R package version 1.14.0. https://CRAN.R-project.org/package=data.table.

6. Wallig, M., Microsoft & Weston, S. 2020. foreach: Provides Foreach Looping Construct. R package version 1.5.0. https://CRAN.R-project.org/package=foreach.

7. Ooi, H., Corporation, M. & Weston, S. 2019. doParallel: Foreach Parallel Adaptor for the 'parallel' Package. R package version 1.0.15. https://CRAN.R-project.org/package=doParallel.

See Also

dataprep::condextr

Examples

percoutl(obsedele(data[c(1:200,3255:3454),c(1:4,27:61)],5,39,4,cores=2),5,39,4,cores=2)
# Result