Bigger is better: Maxing your axis


Last week we talked about enlarging fonts to make them more readable. This week we’re going to apply that same logic to your graph’s y-axis to ensure that any trends are easy to see.

I swear this isn’t about my glasses prescription.

I’m sure we’ve all made a graph in Excel where we selected our data, clicked Insert Chart, and… ended up with a teeny graph smooshed against the x-axis. Recent versions of Excel have gotten a lot better about scaling graphs correctly on the first try, but sometimes your graph still needs that human touch.

Maxing your axis for better dataviz and infographics

Psst – Are you on Pinterest? You know what to do!

 

Start your y-axis at zero

Always.

NO EXCEPTIONS.

But what if my graph has negative values?

FINE. THAT’S THE ONLY EXCEPTION.

 

Find the maximum value in your dataset and then round up

Depending on the quantities you’re working with, this will be the nearest five, ten, hundred, thousand, or some other number with a lot of zeroes. The number of zeroes should reflect the scale of the numbers you’re working with.

making axis scales match your data

In the graph at left, numbers in the hundreds mean your axis should be in the hundreds. The graph at right is in the tens, so the axis ends there too!

You want to end up with a “clean” number (multiple of 10) just larger than the largest number in your dataset. This will allow the data below to stretch to its fullest extent – the larger you draw your data, the more your reader can identify trends.

 

Exception 1: Series of graphs

If you’ve decided to split your spaghetti-impression line graph into a series of individual graphs, be sure to draw these new graphs on the same scale regardless of their contents.

scaling axis for small multiples graphs

In the set on top, all graphs are on the same scale because they’re related. Rescaling graphs (as in the bottom set) would distort these relationships and make visual comparisons incorrect.

 

Exception 2: Graphs on a fixed scale

Say you’re reporting the results of a survey where people were asked to rate something on a scale of 1-10, but everyone gave answers of 5 or below. Bummer.

Normally you’d want to use 5 as the maximum number for your y-axis since it’s nice and clean. But doing so would actually misrepresent your data – a 5 rating would look awesome since its datapoint is up there at the top, when in reality it should be solidly middling.

 

Stretch goals

Really, it’s that simple – by stretching your y-axis from zero to juuuust above the top of your graph, you’ll make your data much easier for your audience to read. Done and done.


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