---
title: "Contour"
description: "2D density contours. What the contour is for, the data it needs and every option it has."
section: "Widgets"
canonical: "https://banksync.io/docs/widgets/chart-contour"
specs: ["dashboards"]
operationBindings: [{"capability":"dashboards","operation":"dashboards.author"}]
---

2D density contours. It sits in the **Correlation** group of the widget library.

![Example contour on a BankSync dashboard](https://cdn.banksync.io/screenshots/docs/charts/contour.b0e0e6d67ed791a2.png)

## When to use it

Use a contour chart to show where pairs of numbers concentrate as smooth, nested regions, like a topographic map. For example, plot transaction amount against day of the month to see typical spending bands. Darker areas hold more points.

## When to pick something else

- Exact counts per region? Use a **Hexbin**.
- Few points, or individual points that matter? Use a **Scatter plot**.
- The spread of a single number? Use a **Density** or **Histogram**.

## The data it needs

Pick these in the **Data** tab of the inspector. BankSync suggests a column for each when your source has an obvious match.

| Field      | Needed   | Pick       | Notes |
| ---------- | -------- | ---------- | ----- |
| **X axis** | Yes      | a number   |       |
| **Y axis** | Yes      | a number   |       |
| **Size**   | Optional | a number   |       |
| **Color**  | Optional | a category |       |

Each row is drawn as it is, so shape the rows first if you need totals. See [Shaping data](/docs/dashboards/dashboards-shaping-data).

## Contour options

This chart has no options of its own; everything on its **Style** tab is the shared chart styling below.

## Shared chart styling

Every chart also has the shared styling options. These apply to this one:

- [Legend](/docs/widgets/chart-styling#legend): position, layout and which series show.
- [Axes](/docs/widgets/chart-styling#axes): titles, tick labels and number format.
- [Grid](/docs/widgets/chart-styling#grid), [title](/docs/widgets/chart-styling#title), [padding](/docs/widgets/chart-styling#padding) and [background](/docs/widgets/chart-styling#background).
- [Value labels](/docs/widgets/chart-styling#value-labels) on the marks.
- [Categories and labels](/docs/widgets/chart-styling#categories-and-labels): top N with "Other", sort order, readable labels, the handwritten callout.
- [Style](/docs/widgets/chart-styling#style): corner radius, line width, opacity and animation.
- [Tooltip](/docs/widgets/chart-styling#tooltip) on hover.
- [Colours](/docs/widgets/chart-styling#palette): follow the dashboard palette or pick one for this chart.

## Messy data

- Both fields must be numbers. Rows where either is blank, text or a date are skipped. If nothing remains you see "No numbers to show".
- Fewer than ten points are drawn as plain dots, since contours from so few points would be misleading.
- The shading shows relative density ("percent of peak"), not amounts or counts.
- Very large tables are sampled evenly before the shape is estimated.
- Outliers stretch the axes and squash the dense region into a small area. Filter them out first.

## On a phone

On a phone the contours smooth over a proportionally wider area and fewer levels are drawn on a shorter card, so the shape reads as a softer blob. The colour key sits under the plot while there is room.

## Related charts

- [Bubble chart](/docs/widgets/chart-bubble): Scatter sized by a field
- [Hexbin](/docs/widgets/chart-hexbin): Binned 2D density
- [Parallel coordinates](/docs/widgets/chart-parallel-coords): Multi-dimensional comparison