{"id":121661,"date":"2007-08-20T22:03:00","date_gmt":"2007-08-20T22:03:00","guid":{"rendered":"http:\/\/www.esri.com\/arcgis-blog\/products\/product\/uncategorized\/organizing-layers-with-too-many-unique-values\/"},"modified":"2007-08-20T22:03:00","modified_gmt":"2007-08-20T22:03:00","slug":"organizing-layers-with-too-many-unique-values","status":"publish","type":"blog","link":"https:\/\/www.esri.com\/arcgis-blog\/products\/product\/mapping\/organizing-layers-with-too-many-unique-values","title":{"rendered":"Organizing layers with too many unique values"},"author":4351,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_searchwp_excluded":""},"categories":[22941],"tags":[38471,31301,34161],"industry":[],"product":[],"class_list":["post-121661","blog","type-blog","status-publish","format-standard","hentry","category-mapping","tag-data-modeling","tag-symbology","tag-unique-values"],"acf":{"short_description":"By Charlie Frye, Esri Chief Cartographer\n\n\n\nIf you make zoning, soils, geology, or any of a number of kinds of maps where your data repre...","flexible_content":[{"acf_fc_layout":"content","content":"

By Charlie Frye, Esri Chief Cartographer<\/strong><\/p>\n

\"\"<\/p>\n

If you make zoning, soils, geology, or any of a number of kinds of maps where your data represent many different types of features, you can make use of some specialized functionality in the unique values symbology method in ArcMap’s layer properties symbology tab.\u00a0 This functionality allows you to create headings within your layer’s symbols that\u00a0will be shown in ArcMap’s table of contents and in your map’s legend.\u00a0 Headings\u00a0provide a shortcut for assigning symbology and add some hierarchy to your table\u00a0contents.\u00a0 Legend headings, at a minimum,\u00a0help visually organize the information in the legend, and if your legend uses\u00a0multiple columns, you can set the column breaks to occur at the headings- this\u00a0makes the legend easier to read.<\/p>\n

There are\u00a0two cases, depending on how your data are organized, where the unique values\u00a0headings functionality will help.\u00a0 First is a case like zoning where you\u00a0may have between 20 and 50 classes of zoning; in this case, the goal is to better\u00a0organize the presentation of those classes by adding some hierarchy to how your\u00a0layer appears in the Table of Contents and the legend.\u00a0 In this first\u00a0case, you can also benefit from using the Match to Symbols in a Style option\u00a0for symbolizing Categories; this automates the assignment of your symbology.\u00a0 Once you use this option, all that remains is\u00a0to assign the headings, which will represent, for the zoning example, the major\u00a0types of zoning, e.g., commercial, residential, public, etc.<\/p>\n

The second\u00a0case is like geology where each map effectively has a unique set of feature\u00a0types, and you may have between 20 and 100 different feature types on a given map,though your data may have more than 1,000 different kinds of features.\u00a0That\u00a0is the map will be showing fewer than the total number of possible feature\u00a0types. For databases with an excessive number of different kinds of features,\u00a0the Match to Symbols in a Style option is not going to be a time saver.\u00a0Instead, setting a different color scheme for each heading is preferred. For\u00a0the geology example, the idea is to show surface geology units by age category\u00a0(quaternary, cretaceous, etc.) using groups of colors that have a narrow hue\u00a0range (see the geology 24K.style for examples).\u00a0 The reason this works\u00a0well is based in how the color schemes are applied to unique values symbology.\u00a0 ArcMap chooses colors from the within the\u00a0color scheme that are as different as possible, making for a visually\u00a0distinctive result.\u00a0 If you don’t like\u00a0the result, just pick the same color scheme again, and you’ll get a different solution\u00a0because the first color is assigned randomly so different color assignments are\u00a0made each time the color scheme is reapplied.<\/p>\n

Here is how\u00a0to add headings to your unique values symbology:<\/p>\n

1.\u00a0 Create\u00a0unique values symbology for your layer<\/a> and then, while still in the Layer\u00a0Properties window’s symbology tab, select several rows that represent features\u00a0that belong in a specific group. Right-click on any of the selected rows to see\u00a0the options that are shown below and choose Move to Heading, then New Heading. You\u00a0can use Ctrl-Click to select multiple rows or Shift-Click to select a range of rows.<\/p>\n

\"Layers<\/p>\n

2.\u00a0 Enter the name of the heading that you want\u00a0to display in the table of Contents and the legend in the resulting dialog box:<\/p>\n

\"Layers<\/p>\n

3. \u00a0Repeat Steps 1 & 2 as needed to\u00a0create additional headings.<\/p>\n

Tips: <\/strong><\/p>\n