# Heatmap

> A dashboard item that draws a grid of cells, one per pair of values on two axes, coloured by a measure on a colour scale.

Source: https://proxus.io/docs/analyze/dashboard-items/heatmap

The **Heatmap**  puts one value in each cell of a grid and colours
it, so patterns across two dimensions stand out: the busy hours of each machine, the weak shifts of each line, the
hot zones of each oven. Use it where a table of numbers is too dense to read and a line chart would need one line per
row.

*Screenshot: The Heatmap with machine utilisation in percent by hour of day from 06:00 to 21:00 for five machines, with the colour scale below the grid*

1. **Axes.** The values of **X Axis** along the bottom and of **Y Axis** down the side, such as hours and machines.
   They appear in the order the data gives them.
2. **Cell.** One pair of axis values, coloured by its **Value**. Hover a cell to see the value.
3. **Colour scale.** The colours from **Min value** to **Max value**. Drag its handles to show only the cells within a
   narrower range.

Select a cell to filter the other items of the dashboard by it, or to drill down if the item has a drill-down set up.
The selected cell gets a dark border.

## Data fields

All three fields are required; without them the item stays empty. **X Axis** and **Y Axis** are read as the text the
field shows, so a date field grouped by hour gives one column per hour. **Value** must be a number; rows without a
value are left out. To put the axes in order, sort the dimensions in the binding.

## Settings

- **Min value** and **Max value** fix the ends of the colour scale. The defaults, 0 and 100, suit percentages. If you
  clear one, the item takes the lowest or highest value in the data.
- **Palette** picks the colours of the scale, from the first colour at the minimum to the last at the maximum.
- **Show Labels** writes the value in each cell.
- **Cell gap** is the width of the border between cells, in pixels.
- **Tooltip decimals** is the number of decimals shown when you hover a cell.
- **X label rotation** and **Y label rotation** turn the axis labels, in degrees, so long labels fit.

## Related

- [Proxus dashboard items](https://proxus.io/docs/analyze/dashboard-items)
- [Use and build dashboards](https://proxus.io/docs/analyze/dashboards)