Rolling Ball Baseline Estimation

## Usage

```
baseline_rollingball(x, y, ...)
# S4 method for class 'numeric,numeric'
baseline_rollingball(x, y, m, s)
# S4 method for class 'ANY,missing'
baseline_rollingball(x, m, s)
```

## Arguments

- x, y
A

`numeric`

vector. If`y`

is missing, an attempt is made to interpret`x`

in a suitable way (see`grDevices::xy.coords()`

).- ...
Currently not used.

- m
An odd

`integer`

giving the window size (i.e. the number of adjacent points to be used; see`window_sliding()`

) for minimization/maximization.- s
An odd

`integer`

giving the window size (i.e. the number of adjacent points to be used; see`window_sliding()`

) for smoothing.

## Value

Returns a `list`

with two components `x`

and `y`

.

## Note

There will be \((m - 1) / 2\) points both at the beginning and at the end of the data series for which a complete \(m\)-width window cannot be obtained. To prevent data loss, progressively wider/narrower windows are used at both ends of the data series.

## References

Kneen, M. A. and Annegarn, H. J. (1996). Algorithm for Fitting XRF, SEM and
PIXE X-Ray Spectra Backgrounds. *Nuclear Instruments and Methods in Physics
Research Section B: Beam Interactions with Materials and Atoms*,
109/110: 209-213. doi:10.1016/0168-583X(95)00908-6
.

## See also

Other baseline estimation methods:
`baseline_asls()`

,
`baseline_linear()`

,
`baseline_peakfilling()`

,
`baseline_polynomial()`

,
`baseline_rubberband()`

,
`baseline_snip()`

## Examples

```
## X-ray diffraction
data("XRD")
## Subset from 20 to 70 degrees
XRD <- signal_select(XRD, from = 20, to = 70)
## Plot spectrum
plot(XRD, type = "l", xlab = expression(2*theta), ylab = "Count")
## Rolling Ball baseline
baseline <- baseline_rollingball(XRD, m = 201, s = 151)
plot(XRD, type = "l", xlab = expression(2*theta), ylab = "Count")
lines(baseline, type = "l", col = "red")
```