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DensityCalculator - Problem with the results

  • 3 February 2020
  • 2 replies
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theodrogo
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Hello everyone,

I have a little problem with the densitycalculator transformer.

Here are the details :

- I want to have the density of a road network into a 1000m*1000m grid

- I've followed the documentation of the densitycalculator transformer and I don't have any results (all the densities are set to 0 in my results)

- I also made a "group by" into the densitycalculator to have the count of road density for each cell of my grid...

 

Do you have any ideas to help me ?

 

Thanks ! :)

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Best answer by markatsafe 7 February 2020, 20:29

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@theodrogo Make sure that the areas and candidates are in the same coordinate system. You will need the Clipper that is disabled in the image you sent so that your _count attribute is on both features - that you use in the Group By.

I've attached an example workspace (2019.2): densitycalculator.fmwt

theodrogo
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Thank you !

My datasets were however in the same coordinate systems, and it still didn't work. I think the problem was the group by (because I didn't merge attributes with the clipper ..).

Finally, I used an alternative method by calculating my road lengths in each cell of approximatively 1km2, then I created a list with the lengths accumulated in each of the cells of the grid, in order to obtain a list of sum, which then allowed me to get my density (by dividing by the total area of each cell) ... In short, I think I did the same work as the transformer "densitycalculator" ... but decomposed way!

Anyway, thank you very much for your answer!

Theo

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