text: import {extent, min, max} from '../../d3_packages.js'
  
  export default function({
    multiData,
    yExtend
  }) {
  
    let extents = []
    multiData.yValues.forEach(v => {
      extent(v).forEach(e => {
        extents.push(e)
      })
    })
  
    if (yExtend) {
      return yExtend
    } else {
      return extent(extents)
    }
  }
  