The chart corresponding to the radar chart, which shows two sets of data: contract amount and amount:

legend: {
        x: 'center',
                 data: ['Contract Amount','Amount'],
        textStyle: {
          color: '#fff'
        }
      },

Set the meaning of each coordinate axis of the radar chart, the position of the coordinate axis, the style of the coordinate axis interval, etc.:

radar: {
        indicator: (function () {
          const res = [
                         {text:'Source', max: 100 },
                         {text:'Other', max: 100 },
                         {text:'Overview Agreement', max: 100 },
                         {text:'Invitation to tender', max: 100 },
                         {text:'Inquiry', max: 100 },
                         {text:'Subscription Agreement', max: 100 },
                         {text:'Negotiate', max: 100 },
                         {text:'Open bidding', max: 100 },
          ];
          return res;
        })(),
                 center: ['68%', '56%'], // Center coordinates of the coordinate axis
                 radius: '58%', // The ratio of the radius of the coordinate axis to the displayable area
                 axisLine: {// coordinate axis style
          lineStyle: {
            color: '#E9EBF1'
          }
        },
                 splitArea: {// The color of the axis separation area: the default is the color of the interval between dark and light, here we set the space between the gaps
          areaStyle: {
            opacity: 0
          }
        }
      },

Set the radar chart data and data display style:

      series: [
        // 1. Contract volume:
        {
                     type:'radar', // radar chart
          data: [
            {
                             name:'Contract volume',
              value: [21.6, 15.9, 40, 23.6, 32.2, 48.7, 18.8, 22.3],
                             emphasis: {// Highlight when the mouse is hovering, and show the data style of the radar chart
                label: {
                  show: true,
                  color: '#fff',
                  fontSize: 14,
                  backgroundColor: '#0D1B42',
                  borderRadius: 5,
                  padding: 3,
                                     shadowBlur: 3 // Shadow width
                }
              }
            }
          ],
          itemStyle: {
                         color: new echarts.graphic.LinearGradient( // set gradient color
              0, 0, 0, 1,
              [
                { offset: 0, color: 'rgba(0, 230, 98, 1)' },
                { offset: 1, color: 'rgba(0, 155, 171, 1)' }
              ]
            )
          },
                     areaStyle: // The style of the radar radiation area
          {
            color: new echarts.graphic.LinearGradient(
              0, 0, 0, 1,
              [
                { offset: 0, color: 'rgba(0, 230, 98, 1)' },
                { offset: 1, color: 'rgba(0, 155, 171, 1)' }
              ]
            )
          },
        },
        
                 // 2. Amount:
        {
          type: 'radar',
          data: [
            {
                             name:'Amount',
              value: [24.0, 42.9, 71.0, 23.2, 22.2, 20.0, 46.4, 32.3],
              emphasis: {
                label: {
                  show: true,
                  color: '#fff',
                  fontSize: 14,
                  backgroundColor: '#0D1B42',
                  borderRadius: 5,
                  padding: 3,
                  shadowBlur: 3
                }
              }
            }
          ],
          itemStyle: {
            color: new echarts.graphic.LinearGradient(
              0, 0, 0, 1,
              [
                { offset: 0, color: 'rgba(1, 184, 252, 1)' },
                { offset: 1, color: 'rgba(100, 74, 255, 1)' }
              ]
            )
          },
          areaStyle:
          {
            color: new echarts.graphic.LinearGradient(
              0, 0, 0, 1,
              [
                { offset: 0, color: 'rgba(1, 184, 252, 1)' },
                { offset: 1, color: 'rgba(100, 74, 255, 1)' }
              ]
            )
          },
        }
      ],

Note that we set the gradient color like this:

new echarts.graphic.LinearGradient( 
              0, 0, 0, 1,
             [
                { offset: 0, color: 'rgba(0, 230, 98, 1)' },
                { offset: 1, color: 'rgba(0, 155, 171, 1)' }
              ]
)

In this way, a radar data display is realized.