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### One-line summary [问题简述] How to change the smoothing of a line chart ### Version & Environment [版本及环境] + ECharts version [ECharts 版本]: "echarts": "4.0.4", "echarts-for-react": "2.0.8" + Browser version [浏览器类型和版本]: Chrome + OS Version [操作系统类型和版本]: Ubuntu 16.04 ### Expected behaviour [期望结果] How can the smoothing formula of a line chart be changed? (So **not** the animation, but the drawing of the line itself) I would like to use something like `quarticOut`  [ Full content available at: https://github.com/apache/incubator-echarts/issues/9020 ] This message was relayed via gitbox.apache.org for [email protected]
