indmax

Finds maximum and its index of an N-dimensional array.

Description

[ind,maxi]=indmax(x)

Finds index to and maximum of N-dimensional array

ind is cell array
maxi is scalar

Example:
r=rand([2 3 4])
[ind,maxi]=indmax(r)
so that
maximum=r(ind{:})

• MATLAB release: MATLAB 7.4 (R2007a)

[w s]

Some comments and questions:

indmax finds the subscripts and not single index. So the function should rather be termed submax.

indmax returns only the first occurrence of max(A). Wouldn't it be better that all indices or subscripts are returned where A==max(A)?

indmax returns the indices (subscripts) as cell array. Wouldn't it be better to return them as row vector? Because this here (taken from your example) returns an error.

A = cat(3,magic(4),flipud(magic(4)+1));
[ind,maxi]=indmax(A)

ind =

    [4] [1] [2]

maxi =

    17

maximum = A(ind)

??? Error using ==> subsindex
Function 'subsindex' is not defined for values of class 'cell'.

[Duane Hanselman]

For an alternative see the functions minn and maxn, file id # 4719, on the File Exchange

[Andreas Hoechner]

dear w s

'So the function should rather be termed submax.'
-yes

'Wouldn't it be better that all indices or subscripts are returned where A==max(A)?' -sometimes, in my case not...

Wouldn't it be better to return them as row vector?'
- not necessarily. and the syntax (see example) is not maximum=A(ind) but maximum=A(ind{:})

anyway, i thought the recursive loop was quite elegant, but of course, using the linear index is faster and easier. i was not aware of maxn by douane hanselman and recommend to use his routine.