maxindc

Purpose

Returns a column vector containing the index (i.e., row number) of the maximum element in each column of a matrix.

Format

y = maxindc(x)
Parameters:x (NxK matrix) – data
Returns:y (Kx1 matrix) – contains the index of the maximum element in each column of x.

Examples

// Generate random x matrix
x = round(rndn(4, 4)*5);

// Find maximum by column
mx = maxc(x);

// Find the indices of the maximums in each column
mxInd = maxindc(x);

If x is equal to:

-2   -8   -1   -2
-1    9    0    7
 9    0    4    8
-2    6    6    1

then

     9            3
mx = 9    mxInd = 2
     6            4
     8            3

Remarks

If x is complex, maxindc() uses the complex modulus (abs(x)) to determine the largest elements.

To find the index of the maximum element in each row of a matrix, transpose the matrix before applying maxindc().

To find the indices of the largest element in a matrix x, use:

colInd = maxindc(maxc(x));
rowInd = maxindc(x[., colInd]);

If there are two or more “largest” elements in a column (i.e., two or more elements equal to each other and greater than all other elements), then maxindc() returns the index of the first one found, which will be the smallest index.

See also

Functions maxc(), minindc(), minc()