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Is there any chance to calculate line lengths by category. To be precise, I have 4 road categories (state, county, local and uncategorized) and want to calculate them all within one poligone.

So far, I could calculate the lengths for all of them together, using Vector>Analysis tools>Basic statistics, in QGIS 2.10.1-Pisa. It provides me with some statistical information, like standard deviation, what I do not need.

Do I have to make 4 shape files for calculate one category of the road, or is there an add-on or a formula to calculate it?

2 Answers 2

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I would probably do the following:

  1. Vector > Data Management Tools > Split Vector Layer

    This splits up your shapefile to 4 separate shapefiles each with a unique category when you select the Unique ID field

  2. Vector > Analysis Tools > Sum Line Lengths

    Then run this tool for each of the 4 shapefiles and your polygon shapefile to get the sum for each category.

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Use the GroupStats plugin, which works like an Excel pivot table and allows you to calculate statistics, such as for length in your case, for various combinations of groups.

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