# Using Axis Equal for Matlab simulation plots of the SIR model gives very flat solution curves

My professor taught us to always use the Matlab command axis equal for our simulation data plots - for all of our homework assignments.

However, in studying the SIR infectious disease model, I'm studying a scaled version, so instead of using population counts I am more conveniently using fractions of populations, so that my vertical y-axis ranges simply from 0 to 1, while the x-axis is for the time domain. Using this approach, and the command axis equal, my data plots look like almost flat lines. When I remove the axis equal command, the solution curves look much closer to the ones given in the news reports, YouTube videos, etc.

My question is: Should I always be using axis equal? And if so, how do I fix my plots so that they look like what we expect to see?

• Why do you think that it's important to use equal axes for quantities whose dimensions (fraction infected vs. time) aren't comparable? Apr 17, 2020 at 5:41

axis equal can be good for some cases, and might be a go-to default for certain kinds of assignments. However, tuning and customizing visualization are also an integral part of scientific research, and proper scales, ticks, grids, view angles, labels are part of that. These tools can be used for both a good purpose (better visualization of a certain phenomenon, a clear indication of a trait) and a bad purpose (deliberately confuse the audience, hide certain aspects). It is important to stay on the "good side".
To sum it up: no, you certainly don't have to use axis equal for all visualization, especially when different axes have incomparable quantities, or even if the scale of the quantities that are comparable are very different.