Causal Systems

  • #1

Main Question or Discussion Point

Hi All,

So I'm at the point where my brain is numb. I've been struggling for the past few hours trying to understand causality. Specifically, I have an input-output relationship y(t) = x(|t|). Determining if this is causal has been very difficult. Causal means that the output at any given time t is dependent on either the current input (present) or past input. So, if I plug in 5 to my output equation, I just get 5. How is that dependent on the past? I'm being told that this system is NOT causal, I.E. dependent on the past, which is really killing me.
 

Answers and Replies

  • #2
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Consider the value of y when the parameter of y is negative. The value would be equal to the value of x with a positive parameter, which you may interpret as the output of the system depending on the future value of the system input.
 
  • #3
jim hardy
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x=y seems present tense.

x=∫y would include past?
 

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