Entering edit mode

Using the Gviz library, I would like to transform data on the fly when plotting. This should be possible using the `DataTrack`

arguments `window`

, `windowSize`

, and `aggregation`

. However, it seems that the `aggregation`

argument is set to `"mean"`

and cannot be changed.

```
library(Gviz)
set.seed(0)
gr <- GRanges(seqnames = "chrI", ranges = IRanges(start = 1:100, width = 1), score = sample(x = 1:100, size = 100, replace = TRUE))
dt <- DataTrack(range = gr, type = "l", name = "Raw data")
dt_mean <- DataTrack(range = gr, type = "l", window = -1, windowSize = 11, aggregation = "mean", name = "aggregate")
dt_max <- DataTrack(range = gr, type = "l", window = -1, windowSize = 11, aggregation = "max", col = "red", lty = "dashed")
dt_min <- DataTrack(range = gr, type = "l", window = -1, windowSize = 11, aggregation = "min", col = "blue", lty = "dotted")
plotTracks(trackList = list(dt, OverlayTrack(trackList = list(dt_mean, dt_max, dt_min))), chromosome = "chrI")
```

When I calculate min and max manually, I get the expected result.

```
library(zoo)
gr_mean <- gr
gr_mean$score <- rollapply(data = gr_mean$score, width = 11, FUN = mean, fill = NA)
dt_manual_mean <- DataTrack(range = gr_mean, type = "l", name = "rollapply")
gr_max <- gr
gr_max$score <- rollapply(data = gr_max$score, width = 11, FUN = max, fill = NA)
dt_manual_max <- DataTrack(range = gr_max, type = "l", col = "red", lty = "dashed")
gr_min <- gr
gr_min$score <- rollapply(data = gr_min$score, width = 11, FUN = min, fill = NA)
dt_manual_min <- DataTrack(range = gr_min, type = "l", col = "blue", lty = "dotted")
plotTracks(trackList = list(dt, OverlayTrack(list(dt_manual_mean, dt_manual_max, dt_manual_min))), chromosome = "chrI")
```

Am I missing something about how to correctly use the `aggregation`

argument or is this a bug?

```
sessionInfo( )
# attached base packages:
# [1] grid stats4 stats graphics grDevices utils datasets methods base
# other attached packages:
# [1] zoo_1.8-9 Gviz_1.38.0 GenomicRanges_1.46.1 GenomeInfoDb_1.30.0 IRanges_2.28.0 S4Vectors_0.32.3 BiocGenerics_0.40.0
```