NOTE: This is the second in my series of “10 things I wish I had known when I started using MATLAB”.

You start out with your nice blank slate of a script and just start adding a few lines. You aren’t sure exactly where you’re going with it, so you just keep adding and adding. Then, you look up and your workspace is full of dozens of variables, some of which have super informative names like “temp” and “data.” Sound familiar? We’ve all been there, believe me!

One of the great things about the MATLAB IDE (integrated development environment) is the workspace and the ability to see at a glance all of your variables, their types, their dimensions and even their contents (for small enough items). But that workspace gets harder and harder to use when its filled with dozens and dozens (don’t judge me!) of variables.

So, what are we to do?

It seems so obvious … just don’t use so many variables. But, like I said, it’s easy to look up and find that you’ve been coding along and filling up your workspace. Don’t worry, there are things you can do to rectify the situation.

There are a couple of things you can do to keep the variable “bloat” down:

• recycle variables
• use arrays
• use structures
• clear variables

Recycle variables

Sometimes you use variables for counting or for holding values temporarily. These are easily “recycled” to be used in a different situation. For example, you have a for loop with a counter i:

for i=1:10
   a(i) = a^i;
end

Later on, you need a loop to do something different, but you don’t need to use a separate variable for the loop counter - just “recycle” i!

x=0.2;
for i=1:40
   taylor(i) = x^i/fact(i);
end

Use arrays to “package” variables

Sometimes you find yourself with a couple of vectors that are all the same dimension. These are easily grouped together into a single array. For example:

names1 = ["Gary", "Donna", "Richard", "Antonia"];
names2 = ["Stephanie", "Raoul", "Herman", "Carter"];
names3 = ["Mary", "Stuart", "Arthur", "Gwendolyn"];

We can replace these by a single array:

names = [names1; names2; names3];

(obviously, the variables names1, names2, names3 are still cluttering up the workspace; but, we can clear them (see below) as long as we don’t need them again)

Use structures to “package” variables

Another way to group variables into a single variable is with the structure variable type. As opposed to the array type, the different elements of a structure don’t have to be of the same type. Each element of the structure is called a field and is accessed through “dot notation.” For example:

people.names = ["Gary", "Donna", "Richard", "Antonia"];
people.ages = [24, 43, 17, 65];
people.state = ["Georgia", "Massachusetts", "New York", "Oregon"];

Now, there is just one variable in the workspace: people, and we can see its contents by typing people at the command line:

Clear variables when you’re done with them

This one is so obvious, but I had been using MATLAB for an embarassinglly long time before I realized I could do this. In fact, to be honest, I learned this trick from grading one of my students’ homework scripts!

If a variable is no longer needed in your script, just clear it and it will be removed from the workspace:

clearvars names1 names2 names3

You can also clear all variables except for certain variables:

clearvars -except people

Just make sure you don’t type clearvars with no variable names because that will clear the entire workspace!