Conditional KPI Cards with Deneb

I’d written a piece recently on exploring the Deneb custom visual for Power BI. In that post I touched on KPI Style visuals. I hadn’t seen much in the way of KPI Style visuals in the Vega-Lite Examples Gallery so I thought I’d revisit them and explore them a little more.

I focused on styles that I’m unable to create with other custom visuals or that I would find difficult to produce in Charticulator. Here are some of the resultant outputs:

One of the most pleasing things about these visuals (aside from the enormous amount of creative freedom I had) was the ability to resize them to be very small compared to native visuals:

Not at all necessary, but satisfying none the same 🙂

The process

Creating the KPI visuals required some forethought. 

There are a number of different ways to achieve a KPI Card as shown, but the following steps outline the approach I took.

To create the KPI chart I would need to layer a few marks like so:

“layer” : [{area}, {line with points}, {circle}, {label 1}, {label 2}]

Layer 1 : Area

For the first layer I would need to declare:

• Mark Type = area
• Colour as constant = light gray
• X mapped to Date field
• Y mapped to Value field
• Remove axes

 "mark": {
	        "type" : "area"
	      },
	      "encoding": {
	        "color": {
	          "value": "lightgray"
	        },
	        "x": {
	          "field": "Date",
	          "type": "temporal",
	          "axis": null
	        },
	        "y": {
	          "field": "Value",
	          "type": "quantitative",
	          "axis": null
	        }
	      }

Layer 2 : Line

For the second layer I would need to declare:

• Mark Type = line with white points and tooltip enabled
• Colour as constant = gray
• X mapped to Date field
• Y mapped to Value field

	{
	      "mark": {
	        "type": "line",
	        "point": {
	          "filled": false,
	          "fill": "white"
	        }, 
	"tooltip" : true
	      },
	      "encoding": {
	        "color": {
	          "value": "gray"
	        },
	        "x": {
	          "field": "Date",
	          "type": "temporal"
	        },
	        "y": {
	          "field": "Value",
	          "type": "quantitative"
	        }
	      }
    },

Layer 3 : Circle

The third layer:

• Mark Type = circle with tooltip enabled
• Colour as conditional = if value is less than target then red else green
• X mapped to the last/maximum Date field value
• Y mapped to Value field for the maximum Date field value

	{
	      "mark": {"type":"circle", "tooltip":true},
	      "encoding": {
	"color": {
	              "condition": {"test": "datum['Value'] < datum['Target']", "value": "red"},
	          "value": "green"},
	        "size": {
	          "value": 30
	        },
	        "x": {
	          "aggregate": "max",
	          "field": "Date",
	          "type": "temporal"
	        },
	        "y": {
	          "aggregate": {
	            "argmax": "Date"
	          },
	          "field": "Value",
	          "type": "quantitative"
	        }
	      }
    },

Layer 4 : Label

The fourth layer:

• Mark Type = text
• X mapped to the maximum Date field value
• Y mapped to Value field for the maximum Date field value, text is from the Formatted Actual field

	        {
	          "mark": {
	            "type": "text",
	            "dx": 0,
	            "dy": -10,
	            "xOffset": 0,
	            "yOffset": 0,
	            "angle": 0,
	            "align": "right",
	            "baseline": "bottom",
	            "font": "sans-serif",
	            "fontSize": 20,
	            "fontStyle": "normal",
	            "fontWeight": "normal",
	            "limit": 0
	          },
	          "encoding": {
	          "x": {
	            "aggregate": "max","field": "Date", "type": "temporal"},
	        "y": {
	          "aggregate": {"argmax": "Date"},"field": "Value", "type": "quantitative"},
	            "text": 
	{"aggregate": {"argmax": "Date"},
	              "field": "Formatted Actual"
	            }
	          }
        },

Labels can be formatted with Vega-Lite, however, I chose to use DAX as I was more familiar with this and I could easily concatenate additional information.

Example DAX:

Formatted Actual = FORMAT([Value],”,##,,.0m”)

Or

Formatted Variance = [Unicode Arrow] & ” ” &[Percentage] & ” ” & [Above/Below] & ” target”

Tidying up the code

There is certainly opportunity to tidy up the code at this point though I am content to leave it as it is.

Border and Background

I set the border from the visual formatting pane to radius of 6. The border and backgrounds could be conditionally formatted using a DAX expression.

Variations

By changing area mark to rule, line mark to circle, the following can be achieved:

By changing argmax and argmin, the highest and lowest values can be highlighted.

To find the min:

	        "x": {
	          "aggregate": {
	            "argmin": "Value"
	          },
	          "field": "Date",
	          "type": "temporal"
	        },
	        "y": {
	          "aggregate": {
	            "argmin": "Value"
	          },
	          "field": "Value",
	          "type": "quantitative"
        }

To find the max:

	        "x": {
	          "aggregate": {
	            "argmax": "Value"
	          },
	          "field": "Date",
	          "type": "temporal"
	        },
	        "y": {
	          "aggregate": {
	            "argmax": "Value"
	          },
	          "field": "Value",
	          "type": "quantitative"
        }

Additional KPI Colours

The Vega-Lite documentation site does not show examples of conditional formatting for more than two values – at least not that I could see. Here’s how to set RAG indicators (which worked for me):

"color" : {"condition": [
{"test": "datum['KPI'] === 2", "value": "red"},
{"test": "datum['KPI'] === 1", "value": "yellow"}
],
"value": "green"}

All in all, I had fun experimenting. I hope you do too 🙂

Kez.