How to calculate in v(k) - v(k-1) in M file

Hi all!

How to calculate v(k) - v(k-1) in M file. v(k) is not in the table/array, but it is an input signal from Simulink model (e.g. voltage) to Matlab Fnc block.

In Simulink (without using Matlab Fnc blocks) I use Variable Transport Delay. But now I want to write as much code as possible in M file.

Thanks.

Answer 1

[Azzi Abdelmalek]

function e=fcn(v)
persistent vp
if isempty(vp)
  vp=0;
end
e=v-vp;
vp=v;

Answer 2

[Wayne King]

you can use the diff() function in MATLAB. That is v(k)-v(k-1)

Also in R2013b if you have DSP System Toolbox, you can use the System object

dsp.FIRFilter

and then use the System block (create Simulink block from the System object)

hfir = dsp.FIRFilter('Numerator',[1 -1]);
 x = 1:10;
 x = x.^2;
 y = step(hfir,x');