sumc

Purpose

Computes the sum of each column of a matrix or the sum across the second-fastest moving dimension of an L-dimensional array.

Format

y = sumc(x)
Parameters:x (matrix or array) – NxK matrix or L-dimensional array where the last two dimensions are \(NxK\)
Returns:y (Kx1 vector or L-dimensional array) – contains the sum of each column, where the last two dimensions are \(Kx1\).

Examples

// Create a 12x1 vector containing an additive sequence
// counting by twos, from 0-22, i.e. 2, 4, 6, 8...22
x = seqa(0, 2, 12);

// Reshape the 12x1 vector 'x' into a 3x4 matrix
x = reshape(x, 3, 4);

// Sum the columns
y = sumc(x);

After the above code, the variables x and y are equal to:

     0  2  4  6
x =  8 10 12 14
    16 18 20 22

    24
y = 30
    36
    42
// Create an additive sequence from 1-24 and reshape it into
// a 2x3x4 array
a = areshape(seqa(1, 1, 24), 2|3|4);

// Sum the columns across the second fastest moving
// dimension
z = sumc(a);

a is a 2x3x4 array such that:

Plane [1,.,.]

      1.0000000     2.0000000     3.0000000     4.0000000
      5.0000000     6.0000000     7.0000000     8.0000000
      9.0000000     10.000000     11.000000     12.000000

Plane [2,.,.]

      13.000000     14.000000     15.000000     16.000000
      17.000000     18.000000     19.000000     20.000000
      21.000000     22.000000     23.000000     24.000000

Variable z is a 2x4x1 array equal to:

Plane [1,.,.]

      15.000000
      18.000000
      21.000000
      24.000000

Plane [2,.,.]

      51.000000
      54.000000
      57.000000
      60.000000

See also

Functions cumsumc(), meanc(), stdc()