be able to plot sub-daily values

[aappling-usgs]

EGRET only plots values stamped with Dates, not date-times (e.g. POSIXct) (#131 (comment)). Loadflex accepts sub-daily resolution; this should be possible with plots, too. Could, however, be as simple [for now] as rounding datetimes to dates, because many of these plots will change only minimally.

[lindsayplatt]

EGRET plotting functions that need to be considered for adapting to subdaily values:

boxConcMonth
plotConcTime
plotConcQ
plotFluxQ
boxQTwice (labeled as "Sampled Days")
multiPlotDataOverview (uses plotConcTime)
plotConcTimeDaily
plotFluxTimeDaily
plotConcPred
plotFluxPred
plotResidPred
plotResidQ
plotResidTime
boxResidMonth
boxConcThree (labeled as "Sampled Days")
plotConcHist
plotFluxHist
fluxBiasMulti (uses plotResidTime, boxQTwice, and boxConcThree )

[lindsayplatt]

All bolded functions are already using DecYear as the value for the x axis, which means they are handling subdaily values. The axis labels could change to reflect this, although, I'm not really sure what they should look like.

@aappling-usgs what do you think the axis labels should be on subdaily plots? Does it depend on how large the total time the axis spans (e.g. range(axis) > 1 year, only show years)?

[lindsayplatt]

There is still one issue because I need to pick one column to use instead of DecYear for plotting. I figured I would just use Date, but that is always a date class thanks to these lines - https://github.com/USGS-R/loadflex/blob/master/R/convertToEGRET.R#L94-L96. dateTime is what reflects the input data, but I can't use that column because it is not a column for regular EGRET data. I could just set the Date column equal to whatever class is coming in, but I want to verify that won't hurt anything else. I will be working on this part tomorrow.

[aappling-usgs]

Yeah, sounds like a problem for a fresh day!