Representing Data - Data Points: Visualization That Means Something - page 115

A descriptive title is a small but easy thing you can create to set up readers
for what they're about to look at. Imagine you produce a time series plot for
gas prices that shows an upward trend. You could just title it “Gas Prices” and
that would be a fair title. That's what it is, but you could also title it “Rising
Gas Prices,” which says what data is used and what is shown. You could also
include lead-in text underneath the title that describes fluctuations or by how
much gas prices rose.

Your choice of visual cues, a coordinate system, and scale can implicitly provide
context. Bright, cheery, and contrasting colors says something different than
dark, neutral, and blending colors. Similarly, a geographic coordinate system
places you within the context of physical space, whereas an x-y plot using
Cartesian coordinates keeps you within a virtual space. A logarithmic scale could
suggest a focus on percentage changes and reduce focus on absolute values.

This is why it's important to pay attention to software defaults.

Note: The people who visualize data best got
to that level because they examined and visual-
ized a lot of data. They gained experience with
each graph made. Reading topics will inform
better decisions, but it's not until you put
what you learn into practice when you really
improve.

Programs are designed to be flexible and fast and they
work outside the context of the data. This is great to draw a
visualization base and explore your data, but it's up to you
to make the right decisions along the way and to make the
computer output something for humans. This comes partly
from knowing how you perceive geometry and colors, but
mostly it comes from practice and the experience gained
from seeing a lot of data and evaluating how others, who
aren't familiar with your data, interpret your work. Common
sense also goes a long way.

PUTTING IT TOGETHER

You know what ingredients are available. Now it's time to cook the meal.
Viewed separately, the visualization components aren't that useful because
they are just bits of geometry floating in an empty space without context.
However, when you put the components together, you get a complete visu-
alization worth looking at.

For example, what do you get when you use length as a visual cue, a Cartesian
coordinate system, and a categorical scale on the horizontal axis and a linear
scale on the vertical? You get a bar chart. Use position with a geographic
coordinate system, and you get points on a map.