# What is a component?

A component is a **saved card**: a filtered result and a design to draw it,
built once and placed on any number of dashboards. *Server errors as a big
number. Requests by method as a pie. Latency as a trend.*

## What it represents

Every card that shows data starts with a dataset and a filter: the **filtered
result**. A component adds **how it looks**: the design, the split, the
colours, what a tap opens.

A card gets its numbers in one of two ways:

- **A dataset, filtered here.** The card has a filter of its own, rolled up
  to one number or kept as rows to split or bucket. Any design.
- **A saved metric.** A filtered result already rolled up to one number, for
  targets and colour rules. Only the single-number designs take a metric; a
  split or a chart needs the rows, so it filters a dataset itself.

A dataset can be behind any number of cards, each with its own filter. One
component can sit on many dashboards; edit it and all update.

## The designs

| Design | Shows |
|---|---|
| **Single stat** | One number, coloured by its rules: a metric, or your own filter. |
| **Grouped stat** | The rows split by a column: the biggest groups as numbers. |
| **Pie, Ranked bars, Bar chart** | The same split: shares of a whole, ranked bars, or columns and bars by size or name. |
| **Trend chart** | The filtered rows over time, by day, week, month or quarter. |
| **Gauge** | One number on a dial, its colour rules as bands. |
| **Table** | The filtered rows, a page at a time: your columns, sortable, with totals. |
| **Goals** | A goal list's first goals and how many are on target. |
| **Calendar** | Upcoming entries from your calendars. |
| **Info card** | A status card an app publishes (staff). |
| **Note** | A heading or a few lines of text. |
| **Menu** | Links in your order, across or down. |

Your project may add designs. One the source can't support is dimmed in the
builder, with the reason: a trend needs a **period column** (the date column
it is read over); a metric offers only the single-number designs.

## How it's set up

**Dashboards → Components → Build a card** opens the builder, with a live
preview beside it.

1. **Where the numbers come from.** *A dataset, filtered here*: pick the
   dataset, build the filter, say how rows roll up, pick the period column.
   **Start from a metric's filter** copies a metric's definition in. Or *a
   saved metric*: pick it.
2. **Pick a design.** A chart picked while on a metric switches to that
   metric's dataset with its filter copied in; it's the card's own from there.
3. **Say what it shows:** what the design needs, such as the split column.
   **Linked cards** here make a click on this card narrow another card on
   the dashboard, or this card narrow to another's clicks.
4. **Style it** (optional): size, number format, unit, colours. A card over a
   metric starts with the metric's.
5. **Drill-down** (optional): the columns a tap opens, ticked and ordered
   beside the rows they'll show. A table's are its own **Columns**.
6. **Name it**, tag it, and choose **Personal** or **Shared**.

Changing the dataset clears options that named a column of the old one; the
builder says which.

## How to use it

- **Place it on a dashboard:** **Edit layout → Add card → Saved card**. A
  dashboard can give it its own title.
- **Find it again** on the Components page: a gallery of live previews, or a
  table with design, source and where it's used; narrow it to a dashboard, a
  dataset or a design.
- **Change it where you see it:** **Edit card** in a card's **⋯** menu opens
  the builder in a window.
- **Split one off.** A card on several dashboards is marked with a link tab;
  **Make a unique copy** makes that placement the dashboard's own.
- **Make it a goal.** A single stat over a metric has **Add to goals**: a goal
  judges a metric. A stat with its own filter is saved as a metric first.

## Good to know

- **You don't need a component for every card.** **Add card** on a dashboard
  places a metric's number, a note or a calendar directly.
- **A card's own filter is its own.** Editing a metric reaches every card
  over that metric, not a card that copied its filter.
- **A shared card draws only a shared metric.** Only staff can share.
- **Deleting a saved card doesn't empty dashboards:** each placement becomes
  an ordinary card.