You can install the released version of themis from CRAN with:
Install the development version from GitHub with:
Following is a example of using the SMOTE algorithm to deal with unbalanced data
library(recipes) library(modeldata) library(themis) data(okc) sort(table(okc$Class, useNA = "always")) #> #> <NA> stem other #> 0 9539 50316 ds_rec <- recipe(Class ~ age + height, data = okc) %>% step_meanimpute(all_predictors()) %>% step_smote(Class) %>% prep() sort(table(bake(ds_rec, new_data = NULL)$Class, useNA = "always")) #> #> <NA> stem other #> 0 50316 50316
Below is some unbalanced data. Used for examples latter.
The following methods all share the tuning parameter
over_ratio, which is the ratio of the majority-to-minority frequencies.
|Random minority over-sampling with replacement||
|Synthetic Minority Over-sampling Technique||
|Adaptive synthetic sampling approach for imbalanced learning||
|Generation of synthetic data by Randomly Over Sampling Examples||
over_ratio = 1 you bring the number of samples of all minority classes equal to 100% of the majority class.
and by setting
over_ratio = 0.5 we upsample any minority class with less samples then 50% of the majority up to have 50% of the majority.
Most of the the following methods all share the tuning parameter
under_ratio, which is the ratio of the minority-to-majority frequencies.
|Random majority under-sampling with replacement||
|Extraction of majority-minority Tomek links||
under_ratio = 1 you bring the number of samples of all majority classes equal to 100% of the minority class.
and by setting
under_ratio = 2 we downsample any majority class with more then 200% samples of the minority class down to have to 200% samples of the minority.
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