# Documentation

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# nanmean

Mean ignoring `NaN` values

## Syntax

```y = nanmean(X) y = nanmean(X,dim) ```

## Description

`y = nanmean(X)` is the `mean` of `X`, computed after removing `NaN` values.

For vectors `x`, `nanmean(x)` is the mean of the remaining elements, once `NaN` values are removed. For matrices `X`, `nanmean(X)` is a row vector of column means, once `NaN` values are removed. For multidimensional arrays `X`, `nanmean` operates along the first nonsingleton dimension.

`y = nanmean(X,dim)` takes the mean along dimension `dim` of `X`.

### Note

If `X` contains a vector of all `NaN` values along some dimension, the vector is empty once the `NaN` values are removed, so the sum of the remaining elements is `0`. Since the mean involves division by `0`, its value is `NaN`. The output `NaN` is not a mean of `NaN` values.

## Examples

Find column means for data with missing values:

```X = magic(3); X([1 6:9]) = repmat(NaN,1,5) X = NaN 1 NaN 3 5 NaN 4 NaN NaN y = nanmean(X) y = 3.5000 3.0000 NaN```