Heatmap

Colour-graded activity grid similar to a GitHub contribution graph. Each cell represents one bucket in a two-dimensional key space. Cell background colour interpolates from the "heatmap/zero" style (no activity) to the "heatmap/max" style (peak activity) based on the cell's fraction of the maximum value in the grid.

Constructor: NewHeatmap(id, class string, rows, cols int) *Heatmap

Methods

• SetValue(row, col int, v float64) — set one cell; calls Refresh
• SetRow(row int, vs []float64) — replace an entire row; calls Refresh
• SetAll(vs [][]float64) — replace the entire grid; panics on dimension mismatch; calls Refresh
• Value(row, col int) float64 — return the value of one cell
• SetRowLabels(labels []string) — set row header strings (nil clears them)
• SetColLabels(labels []string) — set column header strings (nil clears them)
• SetCellWidth(w int) — character width per cell (minimum 1, default 1); width 2 gives square-ish cells on most terminals

Rendering

Each cell is rendered as cellWidth spaces. Background colour is linearly interpolated between "heatmap/zero" background and "heatmap/max" background using lerpColor; the foreground follows the same interpolation.

Cells with value 0 always use the "heatmap/zero" style. The cell(s) equal to the maximum value use the "heatmap/max" style. If all values are 0, every cell uses "heatmap/zero".

Adjacent cells are separated by a single blank character drawn with the base "heatmap" background.

Hint

Width: $\text{labelColW} + \text{cols} \times (\text{cellWidth}+1) − 1$
Height: labelRowH + rows

where labelColW = widest row label + 1 (or 0 if no labels), and labelRowH = 1 if column labels are set, else 0.

Style keys

Selector	Applied to
"heatmap"	Background and border
"heatmap/header"	Row and column label text
"heatmap/zero"	Cells with value 0
"heatmap/mid"	Font for intermediate-value cells
"heatmap/max"	Cells at the maximum value