`diff`

Differences between adjacent elements.

Category: Language Fundamentals > Operators and Elementary Operations

Syntax

Y = diff(X)

Subtracts each element from the one after it along the first non-singleton dimension.

Y = diff(X, n)

Applies the difference n times, giving higher-order differences.

Y = diff(X, n, dim)

Takes differences along dimension dim.

Description

For a vector of length m, diff(x) has length m-1 and entries x(k+1) - x(k). Dividing by the spacing, diff(y) ./ diff(x), approximates the derivative of sampled data. For a matrix the differences run down each column.

If n is at least the length of the working dimension, the result is empty.

Input arguments

X: Numeric array.
n: Order of the difference. The default is 1.
dim: Dimension along which to differentiate.

Output arguments

Y: Differences. The working dimension is shorter by n elements.

Example

x = [1 4 9 16 25];
diff(x)
diff(x, 2)
diff([1 2; 4 8; 9 9])

Output

ans = 1×4

     3     5     7     9
ans = 1×3

     2     2     2
ans = 2×2

     3     6
     5     1

diff