Over a million developers have joined DZone.
Platinum Partner

Why j for Imaginary Unit?

· Big Data Zone

The Big Data Zone is presented by Exaptive.  Learn how rapid data application development can address the data science shortage.

Electrical engineers use j for the square root of -1 while nearly everyone else uses i. The usual explanation is that EE’s do this because they use i for current. But here’s one advantage to using j that has nothing to do with electrical engineering.

The symbols ij, and k are used for unit vectors in the directions of the xy, and z axes respectively. That means that “i” has two different meanings in the real plane, depending on whether you think of it as the vector space spanned by i and j or as complex numbers. But if you use j to represent the imaginary unit, its meaning does not change. Either way it points along the y axis.

Said another way, bold face and italic i point in different directions But bold face j and italic jboth point in the same direction.

Here’s what moving from vectors to complex numbers looks like in math notation:

And here’s what it looks like in electrical engineering notation:

I don’t expect math notation to change, nor would I want it to. I’m happy with i. But using j might make moving between vectors and complex numbers a little easier.

***

By the way, I use j on @DSP_fact. DSP came out of electrical engineering, so j is conventional there. I also use j in Python because that’s what the language requires.

The Big Data Zone is presented by Exaptive.  Learn about how to rapidly iterate data applications, while reusing existing code and leveraging open source technologies.

Topics:

Published at DZone with permission of John Cook , DZone MVB .

Opinions expressed by DZone contributors are their own.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}