GEOG 286 Lecture Notes - Lecture 11: Query Language, Descriptive Statistics, Spatial Analysis
Document Summary
Count: number of values in the dataset. For vector data: start in the attribute table. Statistics tool, statistics for one column for all the features. Summarize tool, statistics calculated for features that share the same value in a column. If a selection is made statistics and summarize tools work only on selected features. For raster data: properties - source- statistics. Queries: extract records in vector layers that meet conditions. In gis software these result in highlighted spatial features and records in the attribute table. They are used to perform basic spatial analysis, create new layers from the selection, and calculate new values in a column for selected records. Aspatial queries: queries focusing on attributes (not spatial characteristics) of vector data. Both spatial and aspatial queries use structured query language (sql) Sql: a special query language used in gis and other softward. Queries can be saved and reused, are nearly always case-sensitive, and used in the select by attributes" tool.
