Estimates the Half-Width at Half-Maximum (FWHM) for a given peak.

## Usage

```
peaks_fwhm(x, y, ...)
# S4 method for numeric,numeric
peaks_fwhm(x, y, center)
# S4 method for ANY,missing
peaks_fwhm(x, center)
```

## 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.

- center
A

`numeric`

value giving the peak position in`x`

units.

## Value

A `numeric`

value.

## See also

Other peaks detection methods:
`peaks_find()`

## Examples

```
## X-ray diffraction
data("XRD")
## Whittaker smoothing
smooth <- smooth_whittaker(XRD, lambda = 1000, d = 2, sparse = TRUE)
## 4S Peak Filling baseline
baseline <- baseline_peakfilling(smooth, n = 10, m = 5, by = 10)
plot(XRD, type = "l", xlab = expression(2*theta), ylab = "Count")
lines(baseline, type = "l", col = "red")
## Correct baseline
XRD <- signal_drift(XRD, lag = baseline, subtract = TRUE)
## Find peaks
peaks <- peaks_find(XRD, SNR = 3, m = 11)
plot(XRD, type = "l", xlab = expression(2*theta), ylab = "Count")
lines(peaks, type = "p", pch = 16, col = "red")
abline(h = attr(peaks, "noise"), lty = 2) # noise threshold
## Half-Width at Half-Maximum
x <- seq(-4, 4, length = 1000)
y <- dnorm(x)
peaks_fwhm(x, y, center = 0) # Expected: 2 * sqrt(2 * log(2))
#> [1] 2.354354
```