stream (version 2.0-1)

DSF_Func: Apply a Function to Transformation to a Data Stream

Description

Applies an R function to transform to a data stream.

Usage

DSF_Func(dsd = NULL, func, ..., info = FALSE)

Value

An object of class DSF_Func (subclass of DSF and DSD).

Arguments

dsd

A object of class DSD.

func

a function that takes a data.frame as the first argument and returns the transformed data.frame.

...

further arguments are passed on to the function specified in func.

info

logical; does the function also receive and modify the info columns?

Author

Michael Hahsler

Details

The function's first argument needs to be a data.frame representing points of the data stream. The function will be called as ps %>% your_function(), where ps is the data.frame with some points obtained using get_points() on the data stream source.

See Also

Other DSF: DSF_Convolve(), DSF_Downsample(), DSF_ExponentialMA(), DSF_Scale(), DSF_dplyr(), DSF()

Examples

stream <- DSD_Gaussians(k = 3, d = 3)
get_points(stream, n = 5)

## Example 1: rename the columns
rename <- function(x, names) {
  colnames(x) <-  names
  x
}

# By default, the info columns starting with . are not affected.
stream2 <- stream %>% DSF_Func(rename, names = c("A", "B", "C"))
stream2
get_points(stream2, n = 5)

## Example 2: add a sum columns
stream3 <- stream2 %>% DSF_Func(function(x) {
  x$sum = rowSums(x)
  x
})
stream3
get_points(stream3, n = 5)

## Example 3: Project the stream on its first 2 PCs (using a sample)
pr <- princomp(get_points(stream, n = 100, info = FALSE))
pca_trans <- function(x) predict(pr, x[, c("X1", "X2", "X3")])[, 1:2 , drop = FALSE]
pca_trans(get_points(stream, n = 3, info = FALSE))

stream4 <- stream %>% DSF_Func(pca_trans)
stream4

get_points(stream4, n = 3)
plot(stream4)

## Example 4: Change a class labels using info = TRUE. We redefine class 3 as noise (NA)
stream5 <- stream %>% DSF_Func(
  function(x) { x[['.class']][x[['.class']] == 3] <- NA; x },
  info = TRUE)
stream5

get_points(stream5, n = 5)
plot(stream5)