1
$\begingroup$

I want to create a function which only accepts integers. if a value other than integers are given it should output zero. This is what I've tried so far. I'm trying to do some discrete time signal experiments like time shifting.

specifically i want to create a function y[n] = u[n] - u[n-5] and create another using it, x[n] = y[n/2] + 2 y[n/2-1/2] so that i can get the following graph,

Here's my copy paste-able code: https://www.wolframcloud.com/objects/a0b8ba05-a8cc-4cae-a075-6435e301d41a

the function i need

enter image description here

Improve this question
$\endgroup$
4
  • 2
    $\begingroup$ For example, use IntegerQ, for example: gamma[n_] := If[IntegerQ[n], (n - 1)!, 0]. You shouls also look at gamma[n_Integer] := (n - 1)!. $\endgroup$
    – Moo
    Dec 10, 2018 at 6:00
  • $\begingroup$ Thank you! so I was able to define y[n_] := If[IntegerQ[n], UnitStep[n] - UnitStep[n - 5], 0] $\endgroup$
    – Ramith Hettiarachchi
    Dec 10, 2018 at 6:20
  • 1
    $\begingroup$ y[_] = 0; y[n_Integer] := UnitStep[n] - UnitStep[n - 5] $\endgroup$
    – Fred Simons
    Dec 10, 2018 at 7:47
  • 1
    $\begingroup$ What about y[n_ /; IntegerQ[n]] := ... $\endgroup$
    – Ulrich Neumann
    Dec 10, 2018 at 9:59

1 Answer 1

Reset to default
1
$\begingroup$

Please upvote my answer if you consider it helpful.

I have been hurt many times.

In your code y[n_Integer] := (UnitStep[n] - UnitStep[n - 5]);, y[n] is only defined when its variable is Integer. That means if the variable of y[n] is a fractional number it outputs nothing. So please refer to my following code:

y[n_] := If[FractionalPart[n] == 0, UnitStep[n] - UnitStep[n - 5], 0]
DiscretePlot[{y[n/2] + 2 y[n/2 - 1/2]}, {n, -2, 12}, PlotRange -> All, PlotStyle -> Directive[PointSize[0.02], Red]]

enter image description here

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.