nanmedian

R2026b

(Not recommended) Median, ignoring NaN values

nanmedian is not recommended. Use the MATLAB^® function median instead. With the median function, you can specify whether to include or omit NaN values for the calculation. For more information, see Version History.

Syntax

y = nanmedian(X)

y = nanmedian(X,"all")

y = nanmedian(X,dim)

y = nanmedian(X,vecdim)

Description

y = nanmedian(X) returns the median of the elements of X, computed after removing all NaN values.

• If X is a vector, then nanmedian(X) is the median of all the non-NaN elements of X.

• If X is a matrix, then nanmedian(X) is a row vector of column medians, computed after removing NaN values.

• If X is a multidimensional array, then nanmedian operates along the first nonsingleton dimension of X. The size of this dimension becomes 1 while the sizes of all other dimensions remain the same. nanmedian removes all NaN values.

y = nanmedian(X,"all") returns the median of all elements of X, computed after removing NaN values.

y = nanmedian(X,dim) returns the median along the operating dimension dim of X, computed after removing NaN values.

y = nanmedian(X,vecdim) returns the median over the dimensions specified in the vector vecdim. The function computes the medians after removing NaN values. For example, if X is a matrix, then nanmedian(X,[1 2]) is the median of all non-NaN elements of X, because every element of a matrix is contained in the array slice defined by dimensions 1 and 2.

Examples

Median of Matrix Data

Find the column medians for matrix data with missing values.

X = magic(3);
X([1 6:9]) = NaN

X = 3×3

   NaN     1   NaN
     3     5   NaN
     4   NaN   NaN

y = nanmedian(X)

y = 1×3

    3.5000    3.0000       NaN

Median Along Vector Dimension

Find the median of a multidimensional array over multiple dimensions.

Create a 3-by-5-by-2 array X with some missing values.

X = reshape(1:30,[3 5 2]);
X([10:12 25]) = NaN

X = 
X(:,:,1) =

     1     4     7   NaN    13
     2     5     8   NaN    14
     3     6     9   NaN    15


X(:,:,2) =

    16    19    22   NaN    28
    17    20    23    26    29
    18    21    24    27    30

Find the median of each page of X by specifying dimensions 1 and 2 as the operating dimensions.

ypage = nanmedian(X,[1 2])

ypage = 
ypage(:,:,1) =

    6.5000


ypage(:,:,2) =

   22.5000

For example, ypage(1,1,1) is the median of the non-NaN elements in X(:,:,1).

Find the median of the elements in each X(:,i,:) slice by specifying dimensions 1 and 3 as the operating dimensions.

ycol = nanmedian(X,[1 3])

ycol = 1×5

    9.5000   12.5000   15.5000   26.5000   21.5000

For example, ycol(4) is the median of the non-NaN elements in X(:,4,:).

Input Arguments

X — Input data

scalar | vector | matrix | multidimensional array

Input data, specified as a scalar, vector, matrix, or multidimensional array.

If X is an empty array, then nanmedian(X) is NaN.

dim — Dimension to operate along

positive integer scalar

Dimension to operate along, specified as a positive integer scalar. If you do not specify a value, then the default value is the first array dimension whose size does not equal 1.

dim indicates the dimension whose length reduces to 1. size(y,dim) is 1 while the sizes of all other dimensions remain the same.

Consider a two-dimensional array X:

• If dim is equal to 1, then nanmedian(X,1) returns a row vector containing the median for each column.

• If dim is equal to 2, then nanmedian(X,2) returns a column vector containing the median for each row.

If dim is greater than ndims(X) or if size(X,dim) is 1, then nanmedian returns X.

vecdim — Vector of dimensions

positive integer vector

Vector of dimensions, specified as a positive integer vector. Each element of vecdim represents a dimension of the input array X. The output y has length 1 in the specified operating dimensions. The other dimension lengths are the same for X and y.

For example, if X is a 2-by-3-by-3 array, then nanmedian(X,[1 2]) returns a 1-by-1-by-3 array. Each element of the output is the median of the elements on the corresponding page of X.

Output Arguments

y — Median values

scalar | vector | matrix | multidimensional array

Median values, returned as a scalar, vector, matrix, or multidimensional array.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• The "all" and vecdim input arguments are not supported.

• The dim input argument must be a compile-time constant.

• If you do not specify the dim input argument, the working (or operating) dimension can be different in the generated code. As a result, run-time errors can occur. For more details, see Incompatibility with MATLAB for Default Dimension Selection (MATLAB Coder).

For more information on code generation, see Introduction to Code Generation for Statistics and Machine Learning Functions and Overview of Code Generation Using MATLAB Coder (MATLAB Coder).

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Refer to the usage notes and limitations in the C/C++ Code Generation section. The same usage notes and limitations apply to GPU code generation.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

• The "all" and vecdim input arguments are not supported.

For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Version History

Introduced before R2006a

R2020b: nanmedian is not recommended

nanmedian is not recommended. Use the MATLAB function median instead. There are no plans to remove nanmedian.

To update your code, change instances of the function name nanmedian to median. Then specify the "omitnan" option for the missingflag input argument.

median offers more extended capabilities for supporting tall arrays, GPU arrays, distribution arrays, and C/C++ code generation.