Create a vector, then compute the differences between the elements.

X = [1 1 2 3 5 8 13 21]; Y = diff(X)

Y =1×70 1 1 2 3 5 8

Note thatYhas one fewer element thanX.

Create a 3-by-3 matrix, then compute the first difference between the rows.

X = [1 1 1; 5 5 5; 25 25 25]; Y = diff(X)

Y =2×34 4 4 20 20 20

Yis a 2-by-3 matrix.

Create a vector and compute the second-order difference between the elements.

X = [0 5 15 30 50 75 105]; Y = diff(X,2)

Y =1×55 5 5 5 5

Create a 3-by-3 matrix, then compute the first-order difference between the columns.

X = [1 3 5;7 11 13;17 19 23]; Y = diff(X,1,2)

Y =3×22 2 4 2 2 4

Yis a 3-by-2 matrix.

Use thedifffunction to approximate partial derivatives with the syntaxY = diff(f)/h, wherefis a vector of function values evaluated over some domain,X, andhis an appropriate step size.

For example, the first derivative ofsin(x)with respect toxiscos(x), and the second derivative with respect toxis-sin(x). You can usediffto approximate these derivatives.

h = 0.001;% step sizeX = -pi:h:pi;% domainf = sin(X);% rangeY = diff(f)/h;% first derivativeZ = diff(Y)/h;% second derivativeplot(X(:,1:length(Y)),Y,'r',X,f,'b', X(:,1:length(Z)),Z,'k')

In this plot the blue line corresponds to the original function,sin. The red line corresponds to the calculated first derivative,cos, and the black line corresponds to the calculated second derivative,-sin.

Create a sequence of equally-spaced datetime values, and find the time differences between them.

t1 = datetime('now'); t2 = t1 + minutes(5); t = t1:minutes(1.5):t2

t =1x4 datetimeColumns 1 through 3 26-Feb-2022 12:12:08 26-Feb-2022 12:13:38 26-Feb-2022 12:15:08 Column 4 26-Feb-2022 12:16:38

dt = diff(t)

dt =1x3 duration00:01:30 00:01:30 00:01:30

diff返回一个durationarray.