In that scenario, all of the elements will have the same color. Using a single color we are able to draw points, lines, polygon borders, or their areas. In hexadecimal form, 00 is interpreted as 0.0 which means a lack of a particular color and FF means 1.0 and shows that the given color has maximal intensity.įor example, #000000 represents black color, #FFFFFF white color, and #00FF00 green color. It consists of six-digits prefixed by the # (hash) symbol, where red, green, and blue values are each represented by two characters. Hexadecimal form, on the other hand, can represent 16,777,216 unique colors. R understands 657 built-in color names, such as "red", "lightblue" or "gray90", that are available using the colors() function. Values of polygons usually cannot be represented by either shapes or sizes, as these two features are connected to the geometries of the objects.Ĭolors in R are created based either on the color name or its hexadecimal form. Similarly, qualitative variables in lines can be presented by different line types. The use of shapes usually should be limited to qualitative variables, and different shapes can represent different categories of points (section 6.3). Quantitative values of line data can be shown with the widths of the lines (section 6.2). Small symbols could represent low values of a given variable, and the higher the value, the larger the symbol. Sizes, on the other hand, should focus on quantitative variables. It can represent both qualitative (categorical) and quantitative (numerical) variables, and also we can color symbols, lines, or polygon fillings (sections 6.1.1 and 6.1.2). The use of visual variables on maps depends on two main things: (a) type of the presented variable, and (b) type of the map layer.įigure 6.1 shows examples of different visual variables.Ĭolor is the most universal visual variable. tmap: elegant and effective thematic maps in RįIGURE 6.1: Basic visual variables and their representations on maps.
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