ML 101: Parameter Versus Variable [MUST KNOW]

Sometimes mistakenly used interchangeably, we’re here to tell you that a parameter is not a variable.

However, depending on the context – a parameter and a variable can mean many different things.

In this post, we’ll break down the following:

  • Difference between a parameter and variable (General)
  • Difference between a parameter and variable (Data Science)
  • An example of both of the above
  • And some frequently asked questions to help solidify the knowledge

Hang on; it’ll be a bumpy ride (at first).

bumpy ride roller coaster


What is the difference between a parameter and a variable?

While these terms are almost used interchangeably, there are some subtle differences.

For example, in a general mathematical equation:

y= mx + b

m and b are the parameters of this equation.

This equation is still “loosely” defined, and once we assign some values to the parameters (like m=4, b=5), the equation is now limited to some domain.

With our equation defined, we now have the following:

y = 4x + 5

We can now pass numbers to our variable (x), as the domain of this function has been set.

While it feels simple, it can still get a little choppy when we extend this idea into computer science.


What is an example of a parameter and variable?

Here we have a parameter of an equation utilizing the same idea as above.

example function

m and b are our parameters, which we can pass any value into.

We have a variable in the equation, which is x = 4.

While we can pass any values into our parameters (arguments), our variable will never change.

Note there are different types of variables called global and local (we go over more about these at the end).

Now that you know the difference between a variable and a parameter in general, We can branch off mathematics and computer science into other related fields.


What is the difference between a parameter and a variable in Data Science?

In data science, the difference between variables and parameters is not similar and is only loosely connected.

In data science, when someone says “variables,” they’re probably referring to your independent variables.

These are the variables commonly used to build models (or multiple models) to predict your dependent variable.

For example, in the image below:

example variables

remote_ratio and company_size would be our independent variables, while salary_in_usd is our dependent variable.
In data science, when someone says “parameters,” they are usually talking about internal model configuration.
Don’t confuse this with hyperparameters, which is a whole other topic.
Here’s an example using linear regression:

dataset and parameters
We have our variables from above, just now one-hot encoded.
We use them to predict our dependent variable, which gives us a model.
And on the bottom, we have the parameters from the model, which in this case, were the coefficients for each variable in our linear regression model.
oh no face

It’s okay, you’ll probably need to re-read that a couple of times.


Frequently Asked Questions

These two terms can get confusing; we hope some of the questions below help clarify things.

Does a variable have parameters?

A variable can have parameters. If a variable is defined as a function, that function could have parameters. A variable does not have to be a function and could just be a scalar (number).

What does it mean when a variable is a parameter?

Sometimes, variables are passed into an equation. In standard software engineering, most teams take a modular approach, which means using functions to solve different parts of code. Many times, variables defined within one function will need to be passed as a parameter to another function, which can happen to many different variables.

Is a parameter a constant or a variable?

A parameter can be a constant or a variable. In Python, you can define parameters with fall-back values, which take the form of variables but can also be constant numbers.

Do variables have parameters in Python?

In Python, variables defined within one function will sometimes need to be passed as a parameter to another function. This can happen to many different variables, all inside one function.

Is a parameter fixed or variable?

Each function fixes parameters. These parameters will not be changed unless someone changes the code. Different variables can be passed to these parameters, changing the local values of the variables.

What makes a value a parameter?

A value becomes a parameter when it’s used to scope some function. It doesn’t matter if it’s in mathematics or computer science; if defining values for part of your equation creates a domain, that value is a parameter.

Are parameters local variables?

Parameters are not local variables. Local variables exist inside functions, which are different from global variables, which are available to all functions everywhere. Many times variables passed into parameters help define these local variables.


More Articles In Our Machine Learning 101 Series

We have many straightforward guides that go over some of the essential parts of machine learning.

Some of those guides include:

      Dylan Kaplan