diff

The C++ interface for diff. More...

array	diff1 (const array &in, int dim=-1)
array	diff2 (const array &in, int dim=-1)

Detailed Description

The C++ interface for diff.

The difference functions compute either the first or second order difference between adjacent elements in an array along a given dimension.

diff1 computes the first order difference (basic adjacent difference) along a given dimension. If the input array has N elements in the dimension of interest, the resulting array has N-1 elements along the given dimension.

array a;     // a = [0 1 2 3 4 5]

print(diff1(a)); // [1 1 1 1 1]

array b; // b = [0 2 4]
         //     [1 3 5]

//Difference along first dimension, down columns
print(diff1(b));   // diff1(b) = [1 1 1]

//Difference alone second dimension, across rows
print(diff1(b,1)); // diff1(b,1) = [2 2]
  a                //              [2 2]

diff2 computes the second order difference (i.e. the difference between the adjacent first order differences) along a given dimension.

float f[] = { 5, 10, 20, 25, 50, 100};
array a(6,1,f); //a = f

// Take diff1 twice
array b = diff1(a); // b = [5 10 5 25 50]
array c = diff1(b); // c = [5 -5 20 25]

//or use diff2 once
array d = diff2(a); // d = c = [5 -5 20 25]

Function Documentation

array af::diff1	(	const array &	in,
		int	dim = -1
	)

Parameters

[in]	in
[in]	dim	dimension along which to operate (-1 indicates first non-singleton dimension)

Returns

difference between neighboring elements

Examples:

examples/pde/fdtd.cpp.

array af::diff2	(	const array &	in,
		int	dim = -1
	)

Parameters

[in]	in
[in]	dim	dimension along which to operate (-1 indicates first non-singleton dimension)

Returns

second order difference between elements