OSSClassif | R Documentation |
This function performs an adapted one-sided selection strategy for multiclass imbalanced problems.
OSSClassif(form, dat, dist = "Euclidean", p = 2, Cl = "smaller", start = "CNN")
form |
A formula describing the prediction problem. |
dat |
A data frame containing the original imbalanced data set. |
dist |
A character string indicating which distance metric to use when determining the k nearest neighbors. See the details. Defaults to "Euclidean". |
p |
A number indicating the value of p if the "p-norm" distance is chosen. Only necessary to define if a "p-norm" is chosen in the |
Cl |
A character vector indicating which are the most important classes. Defaults to "smaller" which means that the smaller classes are automatically determined. In this case, all the smaller classes are those with a frequency below (nr.examples)/(nr.classes). With the selection of option "smaller" those classes are the ones considered important for the user. |
start |
A string which determines which strategy (CNN or Tomek links) should be performed first. The existing options are "CNN" and "Tomek". The first one, "CNN", which is the default, means that CNN strategy will be performed first and Tomek links are applied after. On the other hand, if |
dist
parameter:The parameter dist
allows the user to define the distance metric to be used in the neighbors computation. Although the default is the Euclidean distance, other metrics are available. This allows the computation of distances in data sets with, for instance, both nominal and numeric features. The options available for the distance functions are as follows:
- for data with only numeric features: "Manhattan", "Euclidean", "Canberra", "Chebyshev", "p-norm";
- for data with only nominal features: "Overlap";
- for dealing with both nominal and numeric features: "HEOM", "HVDM".
When the "p-norm" is selected for the dist
parameter, it is also necessary to define the value of parameter p
. The value of parameter p
sets which "p-norm" will be used. For instance, if p
is set to 1, the "1-norm" (or Manhattan distance) is used, and if p
is set to 2, the "2-norm" (or Euclidean distance) is applied.
For more details regarding the distance functions implemented in UBL package please see the package vignettes.
The function returns a data frame with the new data set resulting from the application of the selected OSS strategy.
Paula Branco paobranco@gmail.com, Rita Ribeiro rpribeiro@dcc.fc.up.pt and Luis Torgo ltorgo@dcc.fc.up.pt
Kubat, M. & Matwin, S. (1997). Addressing the Curse of Imbalanced Training Sets: One-Sided Selection Proc. of the 14th Int. Conf. on Machine Learning, Morgan Kaufmann, 179-186.
Batista, G. E.; Prati, R. C. & Monard, M. C. (2004). A study of the behavior of several methods for balancing machine learning training data ACM SIGKDD Explorations Newsletter, ACM, 6, 20-29
TomekClassif, CNNClassif
## Not run:
if (requireNamespace("DMwR2", quietly = TRUE)) {
data(algae, package ="DMwR2")
clean.algae <- data.frame(algae[complete.cases(algae), ])
alg1 <- OSSClassif(season~., clean.algae, dist = "HVDM",
Cl = c("spring", "summer"))
alg2 <- OSSClassif(season~., clean.algae, dist = "HEOM",
Cl = c("spring", "summer"), start = "Tomek")
alg3 <- OSSClassif(season~., clean.algae, dist = "HVDM", start = "CNN")
alg4 <- OSSClassif(season~., clean.algae, dist = "HVDM", start = "Tomek")
alg5 <- OSSClassif(season~., clean.algae, dist = "HEOM", Cl = "winter")
summary(alg1$season)
summary(alg2$season)
summary(alg3$season)
summary(alg4$season)
summary(alg5$season)
}
## End(Not run)
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