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In this lecture, we'll discuss
the idea of using visualization

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to better understand data
and to provide insights

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on the problem we're addressing.

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Why visualization?

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People often say that a picture
is like a thousand words.

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In the same spirit, John
Tukey, a major statistician

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at Princeton, wrote that
"the picture-examining eye

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is the best finder we have
of the wholly unanticipated."

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Visualizing data allows us
to discern relationships,

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structures, distributions,
outliers, patterns, behaviors,

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dependencies, and outcomes.

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Visualization is further useful
for initial data exploration,

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for interpreting models, and
for communicating results

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effectively.

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Let us give some examples
of different modes

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of visualization that
illustrate these points.

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The figure shows
the miles per gallon

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of a car as a function
of the car's weight.

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The figure clearly illustrates
that as the weight of the car

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increases, the miles
per gallon decrease.

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The same graph, but now
colors of the points

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signify the number of cylinders
in the car: four for red,

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six for green,
and eight in blue.

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On the same data, we now
plot a regression line

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that captures the intuition
that as the weight of the car

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increases, the miles
per gallon decrease.

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In this plot, we'll
visualize burglaries

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in the city of Houston by
combining data and geographical

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location in a map.

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This plot illustrates,
using a heat map,

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the usage of rented bicycles
from the Hubway company.

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The horizontal axis is
the hour of the day,

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and the vertical axis the day
of the week, starting on Sunday.

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The heat map shows that
the usage increases

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during the morning and night
rush hours on weekdays.

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The next plot helps us
visualize histograms

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of different categories
using the Hubway data.

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This plot shows US
unemployment by state.

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The lighter colors corresponding
to smaller unemployment,

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and the darker
colors corresponding

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to larger unemployment rates.

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The plan this week is to create
all of these visualizations.

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We'll see how visualizations
can be used to better understand

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data, communicate
information more effectively,

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show the results of
analytical models.

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In the next video, we'll discuss
the World Health Organization,

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and how they use
visualizations effectively.