I'd like to see the browsers in a line chart, just like the visitors. The way browsers are plotted right now doesn't give me any useful information.
If I could see the share of IE6/7 drop over time with a line chart, I could revamp my CSS files and possibly use some HTML5 features. Now that would be useful.
Right now, I'd have to choose a period and compare the pie chart (!) of the last 6 months. Needless to say, I don't do that because it's a chore.
But the data is there, so why not make use of it? Or is the number of data points to be rendered too much to handle?
Thanks for considering,
The first problem is: if there are many browser/version pairs (e.g., 30), then it's a very cluttered line graph. This implies that some filtering must happen (e.g., "Other"), e.g., graph only the top-5.
The next problem then is: what happens when a browser/version pair breaks into the top-5 (or conversely, falls out of the top-5)? Adding more lines to returns us to the first problem.
Well, I was thinking about more condensed browser/version pairs. Why on earth does Piwik differentiate Opera versions 10.62, 10.60, 10.61, 10.53, 10.50 in the first place? That's not really useful. Aren't they essentially the same, except for security patches? That clutters up my stats to a whopping 57 browsers (of which Opera as the browser with a 3% share takes up 15 versions).
But even if you count only major versions, you end up with an estimated 20 versions, that's right.
So the top-5 might be a good idea. As for your question regarding breaking into/falling out of that selected group: From a user standpoint, I'd say if a browser is within the top-5 more than half the time, show it. You could argument that cases like a 50% share for a day and a 1% share on all other days are not shown even though they ought to be. But that case is a bit far-fetched.
From a developer standpoint, I'd say forget that calculation -- it's too expensive. What we could do is look at the beginning, middle and end of the period. Or draw an arbitrary border: Every browser with a current (!) share of at least 5% is shown, and ditch the top-5.
I'm open for more suggestions.
What you are asking is I think two things:
I'll let you create the ticket for "do not count Opera sub versions" if this is relevant.