I have an 18 sector pie chart and would like the label in each sector (within the chart, not outside it) to be orientated towards the centre of the pie chart (like the spokes of a wheel). I'd say this option is probably not available but wonder if anyone has managed to do it?
You are right, this option is not available. A pie chart with 18 segments is pretty much useless from a data visualisation point of view. See here for a powerful demonstration: http://www.perceptualedge.com/articles/08-21-07.pdf
You might be better off using a horizontal bar chart where the text can be placed inside the bars or as labels on the vertical axis.