cummax

Cumulative maximum

Description

example

M = cummax(A) returns the cumulative maximum elements of A. By default, cummax(A) operates along the first array dimension whose size does not equal 1.

• If A is a vector, then cummax(A) returns a vector of the same size containing the cumulative maxima of A.

• If A is a matrix, then cummax(A) returns a matrix of the same size containing the cumulative maxima in each column of A.

• If A is a multidimensional array, then cummax(A) returns an array of the same size containing the cumulative maxima along the first array dimension of A whose size does not equal 1.

example

M = cummax(A,dim) returns the cumulative maxima along the dimension dim. For example, if A is a matrix, then cummax(A,2) returns the cumulative maxima along the rows of A.

example

M = cummax(___,direction) optionally specifies the direction using any of the previous syntaxes. You must specify A and, optionally, can specify dim. For instance, cummax(A,2,'reverse') returns the cumulative maxima of A by working from end to beginning of the second dimension of A.

example

M = cummax(___,nanflag) specifies whether to include or omit NaN values from the calculation for any of the previous syntaxes. cummax(A,'includenan') includes all NaN values in the calculation while cummax(A,'omitnan') ignores them.

Examples

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Find the cumulative maxima of a 1-by-10 vector of random integers.

v = randi(10,1,10)
v = 1×10

9    10     2    10     7     1     3     6    10    10

M = cummax(v)
M = 1×10

9    10    10    10    10    10    10    10    10    10

Find the cumulative maxima of the columns of a 3-by-3 matrix.

A = [3 5 2; 1 6 3; 7 8 1]
A = 3×3

3     5     2
1     6     3
7     8     1

M = cummax(A)
M = 3×3

3     5     2
3     6     3
7     8     3

Find the cumulative maxima of the rows of a 3-by-3 matrix.

A = [3 5 2; 1 6 3; 7 8 1]
A = 3×3

3     5     2
1     6     3
7     8     1

M = cummax(A,2)
M = 3×3

3     5     5
1     6     6
7     8     8

Calculate the cumulative maxima in the third dimension of a 2-by-2-by-3 array. Specify direction as 'reverse' to work from the end of the third dimension to the beginning.

A = cat(3,[1 2; 3 4],[9 10; 11 12],[5 6; 7 8])
A =
A(:,:,1) =

1     2
3     4

A(:,:,2) =

9    10
11    12

A(:,:,3) =

5     6
7     8

M = cummax(A,3,'reverse')
M =
M(:,:,1) =

9    10
11    12

M(:,:,2) =

9    10
11    12

M(:,:,3) =

5     6
7     8

Create a vector containing NaN values and compute the cumulative maxima. By default, cummax ignores NaN values.

A = [3 5 NaN 9 0 NaN];
M = cummax(A)
M = 1×6

3     5     5     9     9     9

If you include NaN values in the calculation, then the cumulative maximum becomes NaN as soon as the first NaN value in A is encountered.

M = cummax(A,'includenan')
M = 1×6

3     5   NaN   NaN   NaN   NaN

Input Arguments

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Input array, specified as a vector, matrix, or multidimensional array. For complex elements, cummax compares the magnitude of the elements. If magnitudes are equal, cummax also compares the phase angles.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | duration
Complex Number Support: Yes

Dimension to operate along, specified as a positive integer scalar. If no value is specified, then the default is the first array dimension whose size does not equal 1.

Consider a two-dimensional input array, A:

• cummax(A,1) works on successive elements in the columns of A and returns an array of the same size as A with the cumulative maxima in each column. • cummax(A,2) works on successive elements in the rows of A and returns an array of the same size as A with the cumulative maxima in each row. cummax returns A if dim is greater than ndims(A).

Direction of cumulation, specified as 'forward' (default) or 'reverse'.

• 'forward' works from 1 to end of the active dimension.

• 'reverse' works from end to 1 of the active dimension.

Data Types: char

NaN condition, specified as one of the following values:

• 'omitnan' — Ignore all NaN values in the input. If the input has consecutive leading NaN values, then cummax returns NaN in the corresponding elements of the output. For example, cummax([NaN 7 13 6],'omitnan') returns the row vector [NaN 7 13 13].

• 'includenan' — Include NaN values from the input when computing the cumulative maxima, resulting in NaN values in the output.

Data Types: char

Output Arguments

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Cumulative maxima, returned as a vector, matrix, or multidimensional array. The size and data type of M are the same as those of A.

Tips

• The 'reverse' option in many cumulative functions allows quick directional calculations without requiring a flip or reflection of the input array.