how to write equation in matlab ?

Answer 1

[KSSV]

If x is your series.

N = length(x) ; 
FI = sum(abs(diff(x)))/N ; 

[Deepu S S]

may i know 'abs' means?

[KSSV]

help abs

 ABS    Absolute value.
    ABS(X) is the absolute value of the elements of X. When
    X is complex, ABS(X) is the complex modulus (magnitude) of
    the elements of X.
 
    See also SIGN, ANGLE, UNWRAP, HYPOT.

    Documentation for abs
       doc abs

    Other functions named abs

       codistributed/abs    duration/abs    iddata/abs    sym/abs
       dlarray/abs          gpuArray/abs

[Deepu S S]

@KSSV how to write the above equation in matlab?

[Image Analyst]

I guess you figured it out since you accepted the answer (remove the division by N), but here is the answer assuming N is the length of the x vector:

FI = sum(abs(diff(x)));

or more accurately, assuming we just want to sum up to N and we have no idea how many elements are in x (might be N or might be something else):

FI = sum(abs(diff(x(1:N))))

[Deepu S S]

Thank you @Image Analyst...now its working