# Causal signals and causal system

• reddvoid
In summary, the conversation discusses the difference between causal signals and causal systems. A causal system relies on present and past inputs for all time, while a non-causal signal exists from -infinity to +infinity and can have values present for t<0. The concept of causality in signals is not as clear as causality in systems due to the arbitrary nature of choosing t=0.
reddvoid
Is there a difference between causal signal and causal system ?
I got this doubt because

consider a system h(t) whose out put depends on present and past inputs only for all t (- infinity to + infinity ) so this system is a causal system

now if we treat this as a signal and since it exists from -infinity to+ infinity so it will be a non-causal signal. . . .

which one is correct ?

Causality in systems makes the most sense. Causality in signals doesn't make that much sense.

Causality in systems determines whether a system relies on future information of a signal x[n+1].

When talking about "causality" in signals, we mean whether they are zero to the left of t=0 or zero to the right of t=0.

A causal signal is zero for t<0
A non-causal zero has values present for t<0.
Anti-causal signals are zero for t>0.

However, the reason why this doesn't really make sense is that if you have a signal, the time t=0 can be chosen arbitrarily.

rajendiran s

Got it :) thank you for clarifying :)

## 1. What is a causal signal?

A causal signal is a measurement or observation that provides evidence of a cause-effect relationship between two variables. It is a signal that suggests that a change in one variable is responsible for a change in another variable.

## 2. How do you differentiate between a causal signal and a spurious correlation?

A causal signal is based on a plausible mechanism or explanation for the observed relationship between two variables, while a spurious correlation is simply a coincidence or random occurrence. To differentiate between the two, it is important to carefully consider the underlying causal mechanism and potential confounding factors.

## 3. What is a causal system?

A causal system is a system in which the output of the system is influenced by the input in a cause-effect relationship. This means that a change in the input will result in a corresponding change in the output, and the system can be described and understood using causal relationships.

## 4. How can causal signals be used in scientific research?

Causal signals can be used to identify and understand cause-effect relationships between variables in scientific research. They can also be used to test hypotheses and theories, and inform decision-making and interventions in various fields such as medicine, psychology, and economics.

## 5. What are some common methods for identifying causal signals?

Experimental designs, such as randomized controlled trials, are often considered the gold standard for identifying causal signals. Other methods include observational studies using statistical techniques, such as regression analysis, to control for potential confounding factors and infer causality.

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