Histogram Widget
Overview
Video
What Is the Histogram Widget?
The Histogram Widget is Datacake’s new, multi-purpose chart component for summarising numeric telemetry across many devices. It combines:
Bar charts – classic column view of each data source.
Interactive statistics table – min | max | average with live highlighting.
Pie charts – first time ever on Datacake! – for quick distribution insights.
Value Ranges – rule-based colouring (and optional grouping in Pie mode).
Use it to visualise anything from city-by-city temperatures to battery-level bands across your fleet.
Quick Start
1
Add Widget → choose Histogram
2
Give it a title (e.g. Temperature Histogram)
3
Open Data tab → add the telemetry fields you want to compare
4
(Optional) set a Unit (°C, %, V, …)
5
Fine-tune look & behaviour under Appearance and Value Ranges
6
Save and resize the widget on your dashboard
Data Configuration
Adding Data Sources
Each bar (or pie slice) starts with a Data Source: pick one or more device fields. Future releases will support semantic shortcuts (e.g. “All temperatures”) – for now, select manually.
Naming & Units
Rename each source for a readable legend label.
Add a Unit so the y-axis, tooltips and statistics table share a consistent suffix.
Appearance Options
Chart Type
Bar Chart (default)
Compare absolute values between sources
Shows value labels above each bar if enabled
Pie Chart
Show distribution (source-based or range-based)
First appearance on Datacake
Switch type anytime in Appearance → Chart Type.
Display Toggles
Show Statistics Table – reveals interactive Min/Max/Avg grid.
Show Values on Bars – numeric labels directly on bars.
Hide Background – transparent widget for dark dashboards.
Decimal Places
Control global rounding (0 – 4 decimals) for bars, tooltips and table cells.
Value Ranges
Value Ranges let you:
Colorise bars or slices according to thresholds.
Group devices into bands when Pie Chart mode is active.
Name
Friendly label (e.g. Cold, Warm, Extreme)
From / To
Inclusive numeric limits
Color
Hex picker for range colour
Enable them under Value Ranges → “Enable Value Ranges”.
Range Colouring (Bar Mode)
Bars keep their individual height (device value) but adopt the colour of the range they fall into – fast visual QA of outliers.
Range Grouping (Pie Mode) – Key Concept
Without ranges, a pie shows one slice per data source. With ranges enabled, the pie swaps to distribution mode:
Each slice is a range, not a device.
Slice size = number of devices inside that range (percentage shown on hover & in legend).
This turns the same telemetry into an instant “how many devices are cold / warm / hot?” insight.
Interactivity
Hover a bar → highlights corresponding row in the statistics table.
Hover a table row → flashes the matching bar.
Hover a pie slice → tooltip with range name + device count + percentage.
Supports real-time updates when the dashboard is in Live Data mode.
Best Practices & Tips
Fleet health distribution
Use Pie + Value Ranges to spot clusters (e.g. battery 0–20 %, 20–50 %, …)
Comparing absolute sensor values
Stick to Bar with value labels and stats table
Many devices (> 20)
Ranges become essential – otherwise the legend gets crowded
Dark dashboards
Enable Hide Background and pick high-contrast range colours
Multi-metric page
Duplicate the widget, then edit Data tab only – ranges & styling carry over
FAQ
Q: Why does my pie chart still show device names instead of ranges?
A: Make sure Enable Value Ranges is toggled on and at least one range is defined.
Q: How are slice percentages calculated?
A: (Device count in range ÷ Total device count) × 100 %. Individual values are not summed in range mode.
Q: Can I disable the statistics table?
A: Yes – Appearance → toggle Show Statistics Table.
Q: Will semantic data selection be available?
A: Yes, upcoming releases will auto-suggest fields (e.g. all “temperature” sensors).
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