# Array formulas

Spreadsheet can display formulas that return an array of values, which spans across multiple cells. This is useful if you want to display dynamic tabular data in the spreadsheet.

Below is a sample Array formula that fetches covid data

```
=IMPORTDATA("https://api.covidtracking.com/v1/us/daily.csv")
```

With the power of Structured references, you can convert this data to table, and start filtering/sorting on this data.

<figure><img src="/files/TqM5urjg0jbRySohniLT" alt=""><figcaption><p>Array formula to structured data</p></figcaption></figure>

## Collision detection

If an array formula tries to overwrite a non-empty cell, a `REF` error is thrown.

## Creating a custom Array formula

Returning a 2-D array from a custom formula function will mark a cell as an array function cell.

```typescript
const MY_FUNCTION = (parser: FormulaParser, arg: FunctionArgument) => {
  return [
    [
      "foo",
      "bar"
    ]
  ]
}
```


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