# xarray.IndexVariable.std

#### IndexVariable.std(dim=None, , skipna=None, ddof=0, \*\*kwargs)[[source]](https://github.com/pydata/xarray/blob/main/xarray/namedarray/_aggregations.py#L558-L637)

Reduce this NamedArray’s data by applying `std` (i.e., standard deviation) along some dimension(s).

* **Parameters:**
  * **dim** ([`str`](https://docs.python.org/3/builtins/stdtypes.html#str), `Iterable` of `Hashable`, `"..."` or [`None`](https://docs.python.org/3/builtins/constants.html#None), *default*: [`None`](https://docs.python.org/3/builtins/constants.html#None)) – Name of dimension[s] along which to apply `std`. For e.g. `dim="x"`
    or `dim=["x", "y"]`. If “…” or None, will reduce over all dimensions.
  * **skipna** ([`bool`](https://docs.python.org/3/builtins/functions.html#bool) or [`None`](https://docs.python.org/3/builtins/constants.html#None), *optional*) – If True, skip missing values (as marked by NaN). By default, only
    skips missing values for float dtypes; other dtypes either do not
    have a sentinel missing value (int) or `skipna=True` has not been
    implemented (object, datetime64 or timedelta64).
  * **ddof** ([`int`](https://docs.python.org/3/builtins/functions.html#int), *default*: `0`) – “Delta Degrees of Freedom”: the divisor used in the calculation is `N - ddof`,
    where `N` represents the number of elements.
  * **\*\*kwargs** (`Any`) – Additional keyword arguments passed on to the appropriate array
    function for calculating `std` on this object’s data.
    These could include dask-specific kwargs like `split_every`.
* **Returns:**
  **reduced** (`NamedArray`) – New NamedArray with `std` applied to its data and the
  indicated dimension(s) removed

#### SEE ALSO
[`numpy.std`](https://numpy.org/doc/stable/reference/generated/numpy.std.html#numpy.std), [`dask.array.std`](https://docs.dask.org/en/latest/generated/dask.array.std.html#dask.array.std), [`Dataset.std`](xarray.Dataset.std.html.md#xarray.Dataset.std), [`DataArray.std`](xarray.DataArray.std.html.md#xarray.DataArray.std)

[Aggregation](../user-guide/computation.html.md#agg)
: User guide on reduction or aggregation operations.

### Notes

Non-numeric variables will be removed prior to reducing. datetime64 and timedelta64 dtypes are treated as numeric for aggregation operations.

### Examples

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```pycon
>>> from xarray.namedarray.core import NamedArray
>>> na = NamedArray("x", np.array([1, 2, 3, 0, 2, np.nan]))
>>> na
<xarray.NamedArray (x: 6)> Size: 48B
array([ 1.,  2.,  3.,  0.,  2., nan])
```

```pycon
>>> na.std()
<xarray.NamedArray ()> Size: 8B
array(1.0198039)
```

Use `skipna` to control whether NaNs are ignored.

```pycon
>>> na.std(skipna=False)
<xarray.NamedArray ()> Size: 8B
array(nan)
```

Specify `ddof=1` for an unbiased estimate.

```pycon
>>> na.std(skipna=True, ddof=1)
<xarray.NamedArray ()> Size: 8B
array(1.14017543)
```

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