MATLAB Function Reference |
Differences and approximate derivatives
Syntax
Description
Y = diff(X)
calculates differences between adjacent elements of X
.
If X
is a vector, then diff(X)
returns a vector, one element shorter than X
, of differences between adjacent elements:
If X
is a matrix, then diff(X)
returns a matrix of row differences:
In general, diff(X)
returns the differences calculated along the first non-singleton (size(X,dim) > 1
) dimension of X
.
Y = diff(X,n)
applies diff
recursively n
times, resulting in the nth difference. Thus, diff(X,2)
is the same as diff(diff(X))
.
Y = diff(X,n,dim)
is the nth difference function calculated along the dimension specified by scalar dim
. If order n
equals or exceeds the length of dimension dim
, diff
returns an empty array.
Remarks
Since each iteration of diff
reduces the length of X
along dimension dim
, it is possible to specify an order n
sufficiently high to reduce dim
to a singleton (size(X,dim) = 1
) dimension. When this happens, diff
continues calculating along the next nonsingleton dimension.
Examples
The quantity diff(y)./diff(x)
is an approximate derivative.
diff(A)
is the first-order difference along dimension 2
.
diff(A,3,4)
is the third-order difference along dimension 4
.
See Also
diary | dir |
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