Perform data resampling
Arguments
- sample_data
a n x 2 data frame is "sample_class" is provided, else, n x 1 data frame of sample IDs
- sample_class
a vector indicates the class of each sample, if != NULL, then stratified sampling is performed
- boot
a logical variable, if TRUE, then perform bootstrap resampling
- sub_ratio
a numerical value between 0 and 1, indicating the subsampling ratio, or NULL