# previousindex¶

## Purpose¶

Returns the index of the previous element or subarray in an array.

## Format¶

pi = previousindex(i, orders)
Parameters
• i (Mx1 vector) – indices into an array where $$M <= N$$.

• orders (Nx1 vector) – orders of an N-dimensional array

Returns

pi (Mx1 vector of indices) – the index of the previous element or subarray in the array corresponding to orders.

## Examples¶

// Set orders
orders = { 3, 4, 5, 6, 7 };

// Initialize array
a = areshape(1, orders);

// Get orders of the array
orders = getorders(a);

// Set starting index
ind = { 2, 3, 1 };

// Get previous index
pi = previousindex(ind, orders);


After the code above, pi is equal to:

      2
pi =  2
5


In this example, previousindex() decremented pi to index the previous 6x7 subarray in array a.

## Remarks¶

previousindex() will return a scalar error code if the index cannot be decremented.