Hard to say without seeing the real data, but I would suggest a pivot table.
If there is too much data for a bar chart to be meaningful then a pie chart would be even more hopeless.
Stephen Few has written some great books on Visualisation and I would recommend them all. He has a particular disdain of Pie Charts that is well worth heeding.
Best Regards, Bill
thanks a lot for your advice!
I would happily read up on visualization - unfortunately it's only partly in my hand: Management has already stated their preferences and going forward they will also do so and, well, at the end of the day it is they who pay my salary, so it's their will that counts... I am not happy with all of it - IMHO, for example, we use too small a fraction of the available screen_space - about 1/3 - to display the actual working data ...
Also, because I am not only designer, but (mainly) developer of the apps (and QlikView_admin, too), I cannot delve too deeply into details. Still, I'd like to. When we have some budget again next year, I'll get some material to read up. I spend a few hrs on the train every day, so there's time.
You're probably right about a pie_chart becoming hard to read - we have employees from approx. 20 different agencies (at the moment).
Still, I think that is the easiest (most visual) way to display that - leaving out the time_dimension and just taking a snapshot from yesterday. - I will give the user some possibility of restricting display to, say, 90% of the total.
Thanks for your answer as well! A line_chart, however, would also become quite hard to read because of the nr. of lines. That's actually a problem in the data, but I have to cope with it somehow...
As Kalyan mentioned, line charts are the most suitable for changes over time. However, with 12 or more different companies it may not be very clear. What you could do is go onto the Dimension Limits tab and only show the most important companies (top 5 ?).
Pie charts are not very helpful for large numbers of slices. Stacked bar chart can be an alternative to line charts but, again, may look rather messy with many companies.
The suggestion of a pivot table is certainly good at displaying the information but isn't ideal for showing trends over time.
So really the solution depends on what you want to focus on. If it is time, then a line chart, if it is volumes then a pivot.
I will close this thread - the fact that decisions on visualization and layout don't altogether lie with me makes this somewhat pointless.
Thanks for the answers anyway!
I agree with you - a linechart or pivottable would probably be best as I cannot restrict and only show the top5 (that would immediately raise questions ;-) - but still I will go with a pie_chart as it is the most "visual", "sexiest" kind of chart to use. It looks a bit confusing with 20 different companies, but I just cannot leave out any data.