Create pie chart

[KuiMing]

1. Create Pie Chart. echart(x,~name, ~value,type='pie')
2. Data removable and calculable.
3. MagicType, restore and saveAsImage was added.

[yihui]

This does not look like a good example in my eyes. Ideally we should not require users to prepare a huge list for echart(), otherwise that defeats the purpose of this package. Instead, we want something as simple as echart(data, ~variable, type = 'pie'). Do you have a better example?

[KuiMing]

Sorry, it's my fault. It was just for testing on my own. I will give a simple example.

[yihui]

Two more things:

1. Please provide some screenshots.
2. Eventually I will need you to clean up the commit history. If you are not very familiar with GIT, I have some instructions here: https://github.com/yihui/knitr/blob/master/CONTRIBUTING.md#pull-requests

Thanks!

[KuiMing]

Improvement according to comment at 2015/5/14

1. give a real example code for pie chart.
2. give a pie.html
3. remove unnecessary code of data.R and echart.R
4. add eConfig and etoolbox in option.R

[KuiMing]

One more thing, I will rebase after you confirm these are ok.

[KuiMing]

Hello Yihui,

Did you check my new code? Is there anything I need to modify?