自定义视觉中的Power BI空白图表

Question

我正在按照本教程为PowerBI创建自定义视觉：http://radacad.com/create-custom-visual-with-r-and-json-part3

假设我在Power BI的自定义外观中使用默认数据：mtcars。我正在尝试创建2个字段，假设"Mileage Per Gallon"和"Cylinder Size"如下：

这是我的 Script.R

source('./r_files/flatten_HTML.r')

############### Library Declarations ###############
libraryRequireInstall("ggplot2");
libraryRequireInstall("plotly")
####################################################

################### Actual code ####################

ValuesWithChangedName <- data.frame(mpgWithChangedName, cylWithChangedName)

p <- plot_ly(ValuesWithChangedName,
  type = 'scatterpolar',
  r = ValuesWithChangedName$mpgWithChangedName,
  theta = ValuesWithChangedName$cylWithChangedName,
  mode = 'markers'
)

####################################################

############# Create and save widget ###############
#p = ggplotly(p);
internalSaveWidget(p, 'out.html');
####################################################

和capabilities.json ：

{
  "dataRoles": [
    {
      "displayName": "Mileage Per Gallon",
      "kind": "GroupingOrMeasure",
      "name": "mpgWithChangedName"
    },
    {
      "displayName": "Cylinder Volume",
      "kind": "GroupingOrMeasure",
      "name": "cylWithChangedName"
    }
  ],
  "dataViewMappings": [
    {
      "scriptResult": {
        "dataInput": {
          "table": {
            "rows": {
              "select": [
                {
                  "for": {
                    "in": "mpgWithChangedName"
                  }
                },
                {
                  "for": {
                    "in": "cylWithChangedName"
                  }
                }
              ],
              "dataReductionAlgorithm": {
                "top": {}
              }
            }
          }
        },
        "script": {
          "scriptProviderDefault": "R",
          "scriptOutputType": "html",
          "source": {
            "objectName": "rcv_script",
            "propertyName": "source"
          },
          "provider": {
            "objectName": "rcv_script",
            "propertyName": "provider"
          }
        }
      }
    }
  ],
  "objects": {
    "rcv_script": {
      "properties": {
        "provider": {
          "type": {
            "text": true
          }
        },
        "source": {
          "type": {
            "scripting": {
              "source": true
            }
          }
        }
      }
    }
  },
  "suppressDefaultTitle": true
}

在这种简单情况下，我没有绘制图表，而是得到了空白图表。 有人可以指出我正在做的错误吗？