walkindex¶
Purpose¶
Walks the index of an array forward or backward through a specified dimension.
Format¶

new_idx =
walkindex
(idx, orders, dim)¶ Parameters:  idx (Mx1 vector of indices into an array) – where \(M <= N\).
 orders (Nx1 vector) – orders of an Ndimensional array
 dim (scalar) – \([1toM]\), index into the vector of indices idx, specifying which dimension to walk through. A positive value will walk the index forward, while a negative value will walk backward.
Returns: new_idx (Mx1 vector of indices) – the new index.
Examples¶
Walk down the columns of a matrix¶
orders = { 4, 3 };
// Starting index
idx = { 1, 1 };
// Get the next index
idx = walkindex(idx, orders, 1);
After the above code, idx will equal:
2
1
If we call it again, like this:
// Starting idx = { 2, 1 }
idx = walkindex(idx, orders, 1);
idx will be changed to:
3
1
We can see that walkindex()
is incrementing the first index by one each time we call it.
Walk down the rows of a matrix¶
We will continue with our example from above, but this time we will change the final input, dim, equal to two to increment the second index.
// Starting idx = { 3, 1 }
idx = walkindex(idx, orders, 2);
idx will be changed to:
3
2
Walk backwards through a 3D array¶
This example decrements the second value of the index vector idx.
orders = { 2, 4, 3 };
idx = { 2, 3, 3 };
idx = walkindex(idx, orders, 2);
2
idx = 2
3
Since the absolute value of the final input, dim was equal to two, the second index was modified. Since the value was negative the index was decremented.
Walk forwards through a 3D array¶
This example will continue with the final value of idx from the previous example.
// Starting idx = { 2, 2, 3 }
idx = walkindex(idx, orders, 3);
Since the final input, dim, is equal to positive three, the third element of idx is increased by one.
2
idx = 2
4
Remarks¶
nextindex()
is often more useful.walkindex()
will return a scalar error code if the index cannot walk further in the specified dimension and direction.
See also
Functions nextindex()
, previousindex()
, loopnextindex