Algorithms For Dummies

Defining How to Draw a Graph

A  few  people  can  visualize  data  directly  in  their  minds.  However,  most  people 

really do need a graphic presentation of the data in order to understand it. This 

point is made clear by the use of graphics in business presentations. You could tell 

others about last year’s sales by presenting tables of numbers. After a while, most 

of your audience would nod off and you’d never get your point across. The reason 

is simple: The tables of numbers are precise and present a lot of information, but 

they don’t do it in a way that people understand.

Plotting the data and showing the sales numbers as a bar chart helps people see 

the relationships between the numbers with greater ease. If you want to point out 

that sales are increasing each year, a bar chart with bars of increasing length 

makes this point quickly. Interestingly enough, using the plot actually presents 

the data in a less accurate way. Trying to see that the company made $3,400,026.15 

last year and $3,552,215.82 this year when looking at a bar chart is nearly impos-

sible. Yes, the table would show this information, but people don’t really need to 

know that level of detail — they simply need to see the annual increase, the con-

trast in earnings from year to year. However, your computer is interested in 

details, which is why plots are for humans and matrixes are for computers.

The following sections help you discover the wonders of plotting. You get a quick 

overview of how plots work with Python. Of course, these principles appear in 

later chapters in a more detailed form. These sections provide a start so that you 

can more easily understand the plots presented later.

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