Creates an interactive 3D plot of PCA scores from the analysis of a
`Spectra`

object, color coded according the to scheme stored in
the object. The plot is created by `plotly`

and appears in a browser window.

```
plot3dScores(
spectra,
pca,
pcs = c(1:3),
ellipse = TRUE,
rob = FALSE,
cl = 0.95,
frac.pts.used = 0.8
)
```

- spectra
An object of S3 class

`Spectra`

.- pca
An object of class

`prcomp`

.- pcs
A vector of three integers specifying the PCA scores to plot.

- ellipse
Logical indicating if confidence ellipses should be drawn.

- rob
Logical; if

`ellipse = TRUE`

, indicates that robust confidence ellipses should be drawn. If`FALSE`

, classical confidence ellipses are drawn.- cl
A number indicating the confidence interval for the ellipse.

- frac.pts.used
If

`ellipse = TRUE`

and`rob = TRUE`

, a number indicating the fraction of the data points to be considered "good" and thus used to compute the robust confidence ellipse.

None. Side effect is a plot in a browser window.

Additional documentation at https://bryanhanson.github.io/ChemoSpec/

```
if (interactive()) {
data(metMUD1)
pca <- c_pcaSpectra(metMUD1, choice = "noscale")
p <- plot3dScores(metMUD1, pca)
p
}
```