7.4.1 Understanding Time Series Forecasts

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "Time Series Forecasting Types",
  "hconcat": [
    {
      "title": "Univariate Forecast: S&P 500 % Change",
      "width": 300,
      "height": 200,
      "layer": [
        {
          "data": {
            "sequence": {
              "start": 0,
              "stop": 30,
              "step": 1,
              "as": "month"
            }
          },
          "transform": [
            {
              "calculate": "datum.month < 24 ? 'Actual' : 'Forecast'",
              "as": "type"
            },
            {
              "calculate": "datum.month <= 24 ? random() * 2 - 1 : datum.month == 24 ? datum.value : random() * 1.5 - 0.75",
              "as": "value"
            }
          ],
          "mark": {
            "type": "line",
            "point": true
          },
          "encoding": {
            "x": {
              "field": "month",
              "type": "quantitative",
              "title": "Month"
            },
            "y": {
              "field": "value",
              "type": "quantitative",
              "title": "% Change"
            },
            "color": {
              "value": "#00497677"
            },
            "strokeDash": {
              "field": "type",
              "type": "nominal",
              "scale": {
                "domain": [
                  "Actual",
                  "Forecast"
                ],
                "range": [
                  [
                    0
                  ],
                  [
                    4
                  ]
                ]
              }
            }
          }
        },
        {
          "data": {
            "values": [
              {
                "month": 24
              }
            ]
          },
          "mark": "rule",
          "encoding": {
            "x": {
              "field": "month",
              "type": "quantitative"
            },
            "color": {
              "value": "blue"
            },
            "size": {
              "value": 2
            }
          }
        }
      ]
    },
    {
      "title": "Multivariate Forecast: Normalized Series",
      "width": 300,
      "height": 200,
      "layer": [
        {
          "data": {
            "sequence": {
              "start": 0,
              "stop": 30,
              "step": 1,
              "as": "month"
            }
          },
          "transform": [
            {
              "calculate": "datum.month < 24 ? 'Actual' : 'Forecast'",
              "as": "type"
            },
            {
              "calculate": "datum.month <= 24 ? random() : datum.month == 24 ? datum.GDP : random() * 0.5 + 0.5",
              "as": "GDP"
            },
            {
              "calculate": "datum.month <= 24 ? random() : datum.month == 24 ? datum['S&P500'] : random() * 0.5 + 0.5",
              "as": "S&P500"
            },
            {
              "calculate": "datum.month <= 24 ? random() : datum.month == 24 ? datum.Unemployment : random() * 0.5 + 0.5",
              "as": "Unemployment"
            }
          ],
          "layer": [
            {
              "mark": {
                "type": "line",
                "point": true
              },
              "encoding": {
                "x": {
                  "field": "month",
                  "type": "quantitative",
                  "title": "Month"
                },
                "y": {
                  "field": "GDP",
                  "type": "quantitative"
                },
                "color": {
                  "value": "#00497677"
                },
                "strokeDash": {
                  "field": "type",
                  "type": "nominal",
                  "scale": {
                    "domain": [
                      "Actual",
                      "Forecast"
                    ],
                    "range": [
                      [
                        0
                      ],
                      [
                        4
                      ]
                    ]
                  }
                }
              }
            },
            {
              "mark": {
                "type": "line",
                "point": true
              },
              "encoding": {
                "x": {
                  "field": "month",
                  "type": "quantitative"
                },
                "y": {
                  "field": "S&P500",
                  "type": "quantitative"
                },
                "color": {
                  "value": "#7F3C8D77"
                },
                "strokeDash": {
                  "field": "type",
                  "type": "nominal",
                  "scale": {
                    "domain": [
                      "Actual",
                      "Forecast"
                    ],
                    "range": [
                      [
                        0
                      ],
                      [
                        4
                      ]
                    ]
                  }
                }
              }
            },
            {
              "mark": {
                "type": "line",
                "point": true
              },
              "encoding": {
                "x": {
                  "field": "month",
                  "type": "quantitative"
                },
                "y": {
                  "field": "Unemployment",
                  "type": "quantitative"
                },
                "color": {
                  "value": "#11A57977"
                },
                "strokeDash": {
                  "field": "type",
                  "type": "nominal",
                  "scale": {
                    "domain": [
                      "Actual",
                      "Forecast"
                    ],
                    "range": [
                      [
                        0
                      ],
                      [
                        4
                      ]
                    ]
                  }
                }
              }
            }
          ]
        },
        {
          "data": {
            "values": [
              {
                "month": 24
              }
            ]
          },
          "mark": "rule",
          "encoding": {
            "x": {
              "field": "month",
              "type": "quantitative"
            },
            "color": {
              "value": "blue"
            },
            "size": {
              "value": 2
            }
          }
        }
      ]
    },
    {
      "title": "Long-Term Forecast: GDP % Change",
      "width": 300,
      "height": 200,
      "layer": [
        {
          "data": {
            "sequence": {
              "start": 0,
              "stop": 84,
              "step": 1,
              "as": "month"
            }
          },
          "transform": [
            {
              "calculate": "datum.month < 60 ? 'Actual' : 'Forecast'",
              "as": "type"
            },
            {
              "calculate": "datum.month <= 60 ? random() * 4 - 2 : datum.month == 60 ? datum.value : random() * 3 - 1.5",
              "as": "value"
            }
          ],
          "mark": {
            "type": "line",
            "point": true
          },
          "encoding": {
            "x": {
              "field": "month",
              "type": "quantitative",
              "title": "Month"
            },
            "y": {
              "field": "value",
              "type": "quantitative",
              "title": "% Change"
            },
            "color": {
              "value": "#00497677"
            },
            "strokeDash": {
              "field": "type",
              "type": "nominal",
              "scale": {
                "domain": [
                  "Actual",
                  "Forecast"
                ],
                "range": [
                  [
                    0
                  ],
                  [
                    4
                  ]
                ]
              }
            }
          }
        },
        {
          "data": {
            "values": [
              {
                "month": 60
              }
            ]
          },
          "mark": "rule",
          "encoding": {
            "x": {
              "field": "month",
              "type": "quantitative"
            },
            "color": {
              "value": "blue"
            },
            "size": {
              "value": 2
            }
          }
        }
      ]
    }
  ]
}