You noticed that we used a lower case x for this one by one matrix.

It's commonly called in mathematics a “scalar”.

And it's common to use lowercase

as the initial value or initial letter in the name of a vector, as we can see from

xvalues up here at the top of the screen and x as we did here for the scalar.

And we used a capital X for a two-dimensional array.

MATLAB knows nothing about that. It's just a custom.

You might, say, maybe, we want an array of voltages.

[CLICKING] Let's give it one, two, three, four, five, six.

I'm in a hurry.

I don't want to come up with any fancy values.

So there's a three by three array of voltages.

If we wanted to say what the first row was, we might say row one,

and I’ll use an underscore to make this clear, of

voltages equals, well, one, two, three.

And I used a lower case r, because this is after all a vector.