How can I subtract elements in an array from the element before it.

DIFF Difference and approximate derivative. DIFF(X), for a vector X, is [X(2)-X(1) X(3)-X(2) ... X(n)-X(n-1)]. DIFF(X), for a matrix X, is the matrix of row differences, [X(2:n,:) - X(1:n-1,:)]. DIFF(X), for an N-D array X, is the difference along the first non-singleton dimension of X. DIFF(X,N) is the N-th order difference along the first non-singleton dimension (denote it by DIM). If N >= size(X,DIM), DIFF takes successive differences along the next non-singleton dimension. DIFF(X,N,DIM) is the Nth difference function along dimension DIM. If N >= size(X,DIM), DIFF returns an empty array. Examples: h = .001; x = 0:h:pi; diff(sin(x.^2))/h is an approximation to 2*cos(x.^2).*x diff((1:10).^2) is 3:2:19 If X = [3 7 5 0 9 2] then diff(X,1,1) is [-3 2 -3], diff(X,1,2) is [4 -2 9 -7], diff(X,2,2) is the 2nd order difference along the dimension 2, and diff(X,3,2) is the empty matrix. See also GRADIENT, SUM, PROD. Documentation for diff doc diff Other uses of diff codistributed/diff iddata/diff tall/diff datetime/diff sym/diff tireModel/diff duration/diff symbolic/diff umat/diff gpuArray/diff tabular/diff