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Documentation> MATLAB API> MISC - vl_localmax

SEL=VL_LOCALMAX(F) returns the indexes of the local maximizers of the Q-dimensional array F.

A local maximizer is an array element whose value is larger than the value of all its neighbors. The neighbors of an element i1...iQ have subscripts j1...jQ such that iq-1 <= jq <= iq (excluding i1...iQ itself). For example, if Q=1 the neighbors of an element are its predecessor and successor in the linear order; if Q=2, its neighbors are the elements immediately to its north, south, west, est, north-west, north-est, south-west and south-est (8-neighborhood).

Points on the boundary of F are ignored (and never selected as local maximizers).

SEL=VL_LOCALMAX(F,THRESH) accepts an element as a mazimizer only if it is not smaller than THRESH.

SEL=VL_LOCALMAX(F,THRESH,P) looks for neighbors only in the first P dimensions of the Q-dimensional array F. This allows to process F in ``slices''.

Remark

  Matrices (2-array) with a singleton dimension are interpreted as vectors (1-array). So for example VL_LOCALMAX([0 1 0]) and VL_LOCALMAX([0 1 0]') both return 2 as an aswer. However, if [0 1 0] is to be interpreted as a 1x2 matrix, then the correct answer is the empty set, as all elements are on the boundary. Unfortunately MATLAB does not distinguish between vectors and 2-matrices with a singleton dimension. To forece the interpretation of all matrices as 2-arrays, use VL_LOCALMAX(F,TRESH,2) (but note that in this case the result is always empty!).

See also: VL_HELP().