Data Visualization

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# Data Visualization
## Graphics output
### Andrew Irwin, <a href="mailto:a.irwin@dal.ca" class="email">a.irwin@dal.ca</a>
### Math & Stats, Dalhousie University
### 2021-03-29 (updated: 2021-03-12)

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# Plan

* Kinds of graphics

* How to describe the size of a graphic

* Knitted documents and separate files

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### Starting figure

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### Kinds of graphics

* Vector graphics (pdf, svg)

* Bitmapped or raster graphics (png, jpeg)

* Why does it matter?
  
  * File sizes
  
  * Quality when printed
  
  * Appearance on screen
  
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### Overview

* Device types: png, ragg, jpeg, svg, pdf

* Size: fig.height, fig.width (in inches, default 7), and fig.asp (aspect ratio: height / width)

* Display size: out.width, out.height (in percentage of display area, e.g., '70%')

* Resolution:  dpi (dots per inch; 96-250 on screen, 300-600 when printed)

* Alignment: fig.align = left, right, center

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### PNG example

Chunk options: `fig.width = 6, fig.asp = 0.65, fig.align="center", out.width = '70%', dev = 'png'`

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### Higher resolution PNG example

Chunk options: `dev='png', dpi=150`

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### RAGG example

Chunk options: `dev='ragg_png', dpi = 150`

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### JPEG example

Chunk options: `dev='jpeg', dpi = 150`

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### SVG example

Chunk options: `dev='svglite'`

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### PDF example

The file looks great on [my computer](33-graphics-output_files/figure-html/pdfoutput-1.pdf) (look in `XXXX_files` folder), but is not shown properly in a web page.

Chunk options: `dev='pdf'`

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# Further reading

* Course notes

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## Task

* No assigned task