on January 7, 2023

Showing Statistics for Multiple Attribute using ‘Show Statistical Summary’ tool in QGIS

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Digging Deeper: Unveiling Hidden Insights with Multi-Attribute Stats in QGIS

QGIS, that trusty open-source Geographic Information System we all know and love, is packed with tools for diving into spatial data. And let’s face it, sometimes you need more than just a surface-level glance. One of the most crucial things you can do is understand the statistics behind your data – seeing how things are distributed, spotting patterns, and ultimately, making smarter decisions based on what you find.

Now, QGIS does have the “Show Statistical Summary” tool. You can find it under View > Statistical Summary or View > Panels > Statistics Panel. It’s handy, sure. It pops up a panel with things like the count, sum, average, median, standard deviation, the smallest value, and the largest value for whatever attribute you pick. But here’s the rub: it only shows you one attribute at a time. And let’s be honest, real-world data analysis rarely boils down to looking at just one thing in isolation. You usually need to juggle multiple attributes to really get the full picture.

So, how do you get around this limitation and wrangle those multi-attribute stats like a pro? Well, you’ve got a few options in your toolbox.

  • The GroupStats Plugin: Your Statistical Sidekick: This plugin is a lifesaver. Think of it as your go-to for generating statistical reports broken down by groups or categories within a field. It lets you calculate all sorts of stats – sums, averages, medians – for multiple attributes, all neatly organized by the values in another attribute field. The results pop up in a table, and you can even export them as a CSV file for some spreadsheet wizardry later on.

  • Batch Mode Stats by Category: Unleash the Power of Repetition: QGIS has a trick up its sleeve: running stats by category in batch mode. Basically, you can tell QGIS to run the same statistical analysis on a bunch of different fields, one after the other. Just add a row for each field you want to analyze, tell it which field to calculate the stats on, and then pick the field(s) you want to group things by. It’ll spit out a separate report for each field. Boom!

  • “Join attributes by location (summary)”: Spatial Stats, Simplified: Need to summarize stats based on where things are located? This tool is your friend. It calculates summary statistics for features based on their spatial relationship with other features. We’re talking counts, maximums, minimums, means, medians – the whole shebang.

  • Field Calculator: Your Data Tinkering Workshop: Don’t underestimate the power of the Field Calculator! It’s not just for simple calculations; you can use it to create entirely new columns based on formulas involving multiple existing columns. For example, you could add up the values from several columns into a single, combined column.

  • Dissolve with Stats / Aggregate Tool: Polygon Power Moves: Got polygon layers? The “Dissolve with Stats” plugin (or the built-in “Aggregate” tool) lets you merge polygons based on a shared attribute while simultaneously calculating statistics for other attributes. It’s perfect for summarizing data within those newly merged shapes.

    • Let’s Get Practical: GroupStats in Action

    Okay, enough theory. Let’s walk through a quick example using the “GroupStats” plugin.

  • Plugin Time: Go to Plugins > Manage and Install Plugins, search for “GroupStats,” and hit that install button.
  • Find Your Plugin: Once it’s installed, you’ll find it somewhere in the QGIS menu, ready to roll.
  • Pick Your Data: In the GroupStats window, select the vector layer you want to work with. Then, drag those attribute fields around to put them in the columns and rows sections. Finally, drag a numeric value into the Value section, and pick the statistic you want to calculate.
  • Crunch the Numbers: Hit “Calculate,” and watch the magic happen.
  • Export and Explore: The results pop up in a table, ready to be exported as a CSV for further analysis.

    • The Takeaway

    While QGIS’s built-in “Show Statistical Summary” tool is a bit limited on its own, the program is far from limited. The plugins and tools that QGIS provides are powerful ways to explore and summarize data. By getting familiar with these techniques, you can unlock deeper insights from your spatial data and make decisions with confidence. So, get out there, experiment, and start digging deeper into your data!

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