Bars and dots: point data

R'de Görselleştirme En İyi Uygulamaları

Nick Strayer

Instructor

What is point data?

One categorical axis, one numeric
Counts, averages, rates, etc.

A single observation

Represents a singular observation of something
E.g. population of a state, rate of cell growth

The bar chart

Popular
Simple
Accurate

ggplot(who_disease) +
  geom_col(aes(x = disease, y = cases))

Not always the best

Bar charts are frequently used when other charts are more appropriate
A few principles can be followed to help avoid this

The stacking principle

Should be used for data that represents a meaningful quantity
Ask: 'Could I stack what I'm measuring to make the bars?'

Why quantities?

"...viewers judge points that fall within the bar as being more likely than points equidistant from the mean, but outside the bar..."

- Scholl & Newman, 2012

People view the bar as 'containing' the values below top
Quantities fulfill this assumption

A big deal?

Not really...
... but alternatives are not worse, so they may as well be used

Let's practice!

R'de Görselleştirme En İyi Uygulamaları

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