Visualizations and the Grammar of Graphics

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# Visualizations and the Grammar of Graphics
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.author[
### INFO 5940 <br /> Cornell University
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# Why visualize data?

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| ID| `\(N\)`| `\(\bar{X}\)`| `\(\bar{Y}\)`| `\(\sigma_{X}\)`| `\(\sigma_{Y}\)`|        `\(R\)`|
|--:|---:|---------:|---------:|------------:|------------:|----------:|
|  1| 142|  54.26610|  47.83472|     16.76983|     26.93974| -0.0641284|
|  2| 142|  54.26873|  47.83082|     16.76924|     26.93573| -0.0685864|
|  3| 142|  54.26732|  47.83772|     16.76001|     26.93004| -0.0683434|
|  4| 142|  54.26327|  47.83225|     16.76514|     26.93540| -0.0644719|
|  5| 142|  54.26030|  47.83983|     16.76774|     26.93019| -0.0603414|
|  6| 142|  54.26144|  47.83025|     16.76590|     26.93988| -0.0617148|
|  7| 142|  54.26881|  47.83545|     16.76670|     26.94000| -0.0685042|
|  8| 142|  54.26785|  47.83590|     16.76676|     26.93610| -0.0689797|
|  9| 142|  54.26588|  47.83150|     16.76885|     26.93861| -0.0686092|
| 10| 142|  54.26734|  47.83955|     16.76896|     26.93027| -0.0629611|
| 11| 142|  54.26993|  47.83699|     16.76996|     26.93768| -0.0694456|
| 12| 142|  54.26692|  47.83160|     16.77000|     26.93790| -0.0665752|
| 13| 142|  54.26015|  47.83972|     16.76996|     26.93000| -0.0655833|

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# The grammar of graphics

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## Grammar

> The whole system and structure of a language or of languages in general, usually taken as consisting of syntax and morphology (including inflections) and sometimes also phonology and semantics.

### Grammar of graphics

* "The fundamental principles or rules of an art or science"
* A grammar used to describe and create a wide range of statistical graphics
* Layered grammar of graphics
    * `ggplot2`

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# Applying the grammar of graphics to an historic data visualization

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## Building Minard's map in R

### `troops`

```
## # A tibble: 51 × 4
##     long   lat survivors direction
##    <dbl> <dbl>     <dbl> <chr>    
##  1  24    54.9    340000 A        
##  2  24.5  55      340000 A        
##  3  25.5  54.5    340000 A        
##  4  26    54.7    320000 A        
##  5  27    54.8    300000 A        
##  6  28    54.9    280000 A        
##  7  28.5  55      240000 A        
##  8  29    55.1    210000 A        
##  9  30    55.2    180000 A        
## 10  30.3  55.3    175000 A        
## # … with 41 more rows
```

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### `cities`

```
## # A tibble: 20 × 3
##     long   lat city      
##    <dbl> <dbl> <chr>     
##  1  24    55   Kowno     
##  2  25.3  54.7 Wilna     
##  3  26.4  54.4 Smorgoni  
##  4  26.8  54.3 Moiodexno 
##  5  27.7  55.2 Gloubokoe 
##  6  27.6  53.9 Minsk     
##  7  28.5  54.3 Studienska
##  8  28.7  55.5 Polotzk   
##  9  29.2  54.4 Bobr      
## 10  30.2  55.3 Witebsk   
## # … with 10 more rows
```

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## Minard's grammar

* Troops
    * Latitude
    * Longitude
    * Survivors
    * Advance/retreat
* Cities
    * Latitude
    * Longitude
    * City name
    
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* Layer
    * Data
    * Mapping
    * Statistical transformation (stat)
    * Geometric object (geom)
    * Position adjustment (position)
* Scale
* Coordinate system
* Faceting

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