Help coloring Deneb heatmap

Hey Doug7983. Welcome to the forums! That's awesome that you're diving into Deneb. Thank you for providing your spec and screenshots. Here's how to provide a .pbix, which would be very helpful. Alternatively, if you're able to provide a sanitized dataset that matches your schema, that will also work. 

Happy to try to help once I have either the dataset or .pbix. 

Thanks for the dataset, Doug7983. Let me know if something like this scratches the itch.
Here is a gist that contains the spec. I've also included it below.

{
  "resolve": {"scale": {"color": "independent"}},
  "facet": {
    "row": {
      "field": "Category",
      "header": {"labelAngle": 0, "labelAlign": "left"},
      "title": null
    }
  },
  "spacing": -5,
  "spec": {
    "mark": {"type": "rect", "stroke": "white", "tooltip": true},
    "encoding": {
      "x": {
        "field": "Date",
        "type": "ordinal",
        "title": null,
        "timeUnit": "yearmonth",
        "axis": {
          "domain": false,
          "ticks": false,
          "labels": true,
          "labelAngle": -90,
          "orient": "top"
        }
      },
      "tooltip": [
        {"field": "Category", "type": "nominal"},
        {"field": "Date", "type": "ordinal"},
        {"field": "Growth (MoYaM)", "type": "quantitative", "format": ".1%"},
        {"field": "Growth (WDC)", "type": "quantitative", "format": ".1%"}
      ],
      "color": {
        "aggregate": "max",
        "field": "Growth (WDC)",
        "type": "quantitative",
        "title": "Growth (WDC)",
        "legend": {
          "direction": "horizontal",
          "title": null,
          "gradientLength": 120,
          "format": ".1%",
          "labelOffset": {"expr": "-child_height*0.6"},
          "labelColor": {
            "expr": "luminance(scale('child_color', max(0, parseFloat(datum.label)/100))) < 0.5 ? '#fff' : '#000'"
          }
        }
      }
    }
  },
  "data": {
    "name": "dataset"
   }
  }
}

Hey Doug7983, I'm only providing the values in the values array in the gist for example purposes. You can see that in the embedded spec (not the gist) I left that array out. Deneb assumes that you have named your data "dataset", and will receive the values dynamically from Power BI.

In the example that I provided, each row is independent from one another color-wise and thus has its own legend. That's why the lightest color for one row has a different minimum input domain (lowest value) than that of another row. If you were to go to the gist and comment out the following line:

  "resolve": {"scale": {"color": "independent"}},

then the legend would no longer be independent for each row.

(color domains and legends are independent per row)

vs.

(color domain and legend are shared across entire dataset)

Forgive me, but I'm having trouble understanding. I'm confused about what you're trying to achieve because this:

My data has a range of -12.4% to 64.8%:

The deepest blue will always correspond to the highest value in the data set, regardless of row.

The deepest orange will always correspond to the lowest value in the data set, regardless of row.

The spectrum of color is applied such that a particular shade of blue, for example, will represent the same value, no matter where it appears. Same for shades of orange and everything in between. 

seems to conflict with:

I’m new to Deneb and haven’t been able to figure out how to color this heatmap so that it is colored by row, or category, rather than as a whole:

<.png>

I want the rows to be color independently

 
For example, if the deepest blue will always correspond to the highest value in the data set regardless of row, the heatmap would not be colored independently.

Hey Doug7983, let me know if this is any closer. Note - you can eliminate the spacing between the FYs by setting the column spacing to -5.

Here's the gist.

Here's the spec:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "transform": [{"calculate": "'FY ' + year(datum['Date'])", "as": "FY"}],
  "facet": {
    "column": {"field": "FY", "title": null, "header": {"labelFontSize": 13}}
  },
  "resolve": {"scale": {"x": "independent"}},
  "spacing": {"column": 5},
  "spec": {
    "width": {"step": 30},
    "mark": {"type": "rect", "stroke": "white", "tooltip": true},
    "encoding": {
      "x": {
        "field": "Date",
        "type": "ordinal",
        "title": null,
        "timeUnit": "month",
        "axis": {
          "domain": false,
          "ticks": false,
          "labels": true,
          "labelOpacity": 0.65,
          "orient": "top"
        }
      },
      "y": {
        "field": "Category",
        "type": "nominal",
        "title": "",
        "axis": {
          "domain": false,
          "ticks": false,
          "labels": true,
          "labelOpacity": 0.65,
          "labelAngle": 0,
          "labelPadding": 5
        }
      },
      "tooltip": [
        {"field": "Category", "type": "nominal"},
        {"field": "Date", "type": "ordinal"},
        {"field": "Growth (MoYaM)", "type": "quantitative", "format": ".1%"},
        {"field": "Growth (WDC)", "type": "quantitative", "format": ".1%"}
      ],
      "color": {
        "aggregate": "max",
        "field": "Growth (WDC)",
        "type": "quantitative",
        "title": "Growth (WDC)",
        "scale": {"domainMid": 0, "reverse": true, "scheme": "blueorange"},
        "legend": {
          "titleBaseline": "bottom",
          "direction": "vertical",
          "format": ".1%",
          "orient": "right"
        }
      }
    }
  },
  "data": {
    "name": "dataset"
  }
}

Doug7983, dang, that's no good. What does the date tooltip say for cells in this column? I can see if I can recreate it on my end

Doug7983, no problem! Sorry it took so long for me to comprehend what you were after, but glad we got it in the end. Feel free to tag me in any future posts if you have any Deneb related questions. Always happy to get some vega/vega-lite practice in.