Concur! I was totally biting my tongue and not saying this because I didn’t want to complain, nor to give extra work to Gareth, but it is really easy for people to misunderstand representations which show an incomplete bucket in the same visual way that it shows complete buckets (Figure A below).
Here’s are a couple of ideas for better representation — no idea how much work it would be to implement in this case:
Whenever you’re visually representing a series of buckets as stacked bar charts, and you have an incomplete bucket (like a month that is not yet over) as one of them, make that one thinner proportionally to how incomplete it is. Like, if we’re halfway through the month, make that bar be half as wide as the bars representing complete months. Maybe show a dotted line showing how wide it will be at the end of the month. (Figure C)
Another related concept is show a dotted-line linear extrapolation, i.e. if you’re halfway through the month, and you have 1000 items in the bucket, then show the 1000 items in the same color as the items from completed buckets (previous months), plus show a dotted line outline to indicate that, if the same rate holds for the rest of the month, that there will probably be 2000 items in this bucket by the end of the month. (Figure D)
Might be possible to combine both ideas.
Just some thoughts. Would be curious what Gareth thinks. Obviously it would be easier to just do what Daira suggested and omit incomplete buckets from your visualization. That would definitely be better, IMHO, than showing incomplete buckets side by side and visually identical to complete buckets. You could perhaps show the latest, incomplete bucket separately somehow, so that it is visually distinct from the complete buckets. (Figure B)
P.S. Ooh, you could even conceivably have that last, incomplete bucket be a dotted-line outline which is partially filled with mini-buckets. For example, if the last bucket is a month that is halfway over, it could be a dotted line that is one-month-wide, and it could have 15 little mini-bar-charts in it each of which is 1/30th of a month wide, showing the 15 days that have already passed and already have data. i think that should result in a visual indicator to the reader that both (a) shows them that this isn’t the same kind of data as the complete-buckets-data, and (b) gives them an indication or a prediction of where it is likely to end up. (Figure E)
P.P.S. This is probably a job for whoever makes the graphing libraries that Gareth is using rather than a job for Gareth.