I would like to use the `DataTrack` (generic function from `plot`) with `types` as exemplified in script below. My real data contain a lot of `NA` values, thus I modified the `Gviz` package example to expose my problem.

First, this is how the plot looks like without NAs:

    library(Gviz)
    
    ## Loading GRanges object
    data(twoGroups)
    
    ## Plot data without NAs
    dTrack <- DataTrack(twoGroups, name = "uniform")
    tiff("Gviz_original.tiff", units="in", width=11, height=8.5, res=200, compress="lzw")
    plotTracks(dTrack, groups = rep(c("control", "treated"),
    each = 3), type = c("a", "p", "confint"))
    graphics.off()

  [1]: http://i.stack.imgur.com/53AI6.png

Now, the plot with NAs:

    ## Transforming in data frame
    df <- as.data.frame(twoGroups)
    
    ## Input NAs to look like my real data
    df[ df <= 0 ] = NA
    df <- df[,-4]
    df <- df[,-4]
    names(df) <- c("chr", "start", "end", "control", "control.1", "control.2", "treated", "treated.1", "treated.2")
    
    ## Plot with NA
    df <- makeGRangesFromDataFrame(df, TRUE)
    dftrack <- DataTrack(df, name = "uniform")
     tiff("Gviz_NA.tiff", units="in", width=11, height=8.5, res=200, compress="lzw")
    plotTracks(dftrack, groups = rep(c("control", "treated"),
     each = 3), type = c("a", "p", "confint"))
    graphics.off()

 [2]: http://i.stack.imgur.com/66JJa.png

I am aware that each graphic is from a different data now. However, even in the plot with NAs I expect lines relying on the means (even if the mean is estimated from just 1 animal!). Any ideas why the lines are not completely there? Thank you!

Note that plotTracks() has an ellipsis (...) argument, which allows you to pass arbitrary arguments to lower level functions (so long as they have ellipsis arguments as well). As an example, the mean() function by default uses an argument of na.rm = FALSE, so any vector with NA observations will have a mean of NA as well.

> mean(c(1,2,NA,4,5,6))
[1] NA
> mean(c(1,2,NA,4,5,6), na.rm = TRUE)
[1] 3.6

If you then modify your call to plotTracks() by adding na.rm = TRUE, then  you will calculate means even if there are NA observations. But since you need more than one observation to get a CI, you just get the lines, not the CI bands.

plotTracks(dftrack, groups = rep(c("control", "treated"),
     each = 3), type = c("a", "p", "confint"), na.rm = TRUE)

Edit:  It is more likely that the code that computes the confidence intervals does not have an 'na.rm' argument, which is why you don't get a CI band, rather than the number of observations that are not NA.