Many times in my wiki documents we need to show comparative data (in my concrete case we use charts to show the speed in different versions of our product). Now we are making it with LibreOffice Calc -> save as an image -> upload the image file -> and insert the file in the wiki.

This leaves us with accessibility problems and primary with usability problems as we need to use other application to make the charts and you only get an image without interactive data (show value when hover with the mouse). We normally don't have complex charts so they are easy to be write by hand and then they can fit into Remarkup language.

Other famous wikis sites already have it (for example, read http://en.wikipedia.org/wiki/Wikipedia:Graphs_and_charts).

I think that isn't needed to have many types of graphs, but at least pie and column ones must be necessary as they represent different things that are very common (fractions of a whole and comparative data).

The sintax can be something easy like in Wikipedia, for example:

{{Pie chart
|other = yes
|value1 = 27
|label1 = One
|value2 = 32
|label2 = Two
|value3 = 12
|label3 = Three
|value4 = 9
|label4 = Four}}

Other way can be the possibility to save and store as other object (other application) as images and only reference it like other objects, for example:

{C133} To insert the chart 133.

Facts application can generate charts so I think that something of it can be reused to implement this.