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Subsections

PROD Product Function

Usage

Computes the product of an array along a given dimension. The general syntax for its use is

   y = prod(x,d)

where x is an n-dimensions array of numerical type. The output is of the same numerical type as the input, except for integer types, which are automatically promoted to int32. The argument d is optional, and denotes the dimension along which to take the product. The output is computed via

$\displaystyle y(m_1,\ldots,m_{d-1},1,m_{d+1},\ldots,m_{p}) =
\prod_{k} x(m_1,\ldots,m_{d-1},k,m_{d+1},\ldots,m_{p})
$

If d is omitted, then the product is taken along the first non-singleton dimension of x.

Example

The following piece of code demonstrates various uses of the product function

--> A = [5,1,3;3,2,1;0,3,1]
A = 
  <int32>  - size: [3 3]
 
Columns 1 to 3
             5              1              3  
             3              2              1  
             0              3              1

We start by calling prod without a dimension argument, in which case it defaults to the first nonsingular dimension (in this case, along the columns or d = 1).

--> prod(A)
ans = 
  <int32>  - size: [1 3]
 
Columns 1 to 3
             0              6              3

Next, we take the product along the rows.

--> prod(A,2)
ans = 
  <int32>  - size: [3 1]
 
Columns 1 to 1
            15  
             6  
             0



Samit K. Basu 2005-03-16