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So I'm just trying to make a heatmap based on 13 points I have which are the centroids for 13 regions in a country. The attribute of 'water percentage' is what I would like to base the heat map off of.

I've been working on this in arcgis with no love for some time. (Not enough points to create a strong krig or IDW output), Kernel density yielded a nice output but wouldn't allow me to extend the output further, past the points extent so it wouldn't cover my whole country boundary (geoprocessing>environments>processing extent; data frame set extent; properties>extent>set extent to another layer; etc. --nothing would actually change it). See Arcmap image below:

enter image description here

So I tried QGIS (which I have never used before) because I saw they had an easy option for making heat maps. I cannot use the heat map plugin because my data is vector (13 points) not raster.

What I've done is added my points as a point layer, went to properties>style, and changed it from single symbol to heat map. I get a nice output which looks good enough (still working to make it look more accurate)

enter image description here

**The problem is I need to clip this output to my country boundary and I can't seem to do this. I save it but it only shows up as a points layer again, without the style formatting. How may I clip the style formatting?

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    Also (just for background), I have this water percentage data for 3 different years so I will be reproducing this method for the latter two years to make a panel showing all 3 years and how flood extent has changed over time. – mk24 Mar 17 '16 at 18:07
  • Do you need the clip for display purposes or for data sharing? (It's possible to create a simple mask solely for display purposes) – underdark Mar 17 '16 at 18:39
  • I'm not quite sure what you mean by 'data sharing', but yes, I just need the clip for display purposes. How would I create this mask? – mk24 Mar 17 '16 at 18:42
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    Move the country boundary layer to the top and style it using an inverted polygon renderer gis.stackexchange.com/questions/153754/… – underdark Mar 17 '16 at 20:11
  • The inverted polygon renderer was exactly what I needed! What an interesting work-around. Thank you so much for this suggestion! – mk24 Mar 21 '16 at 14:37
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Save your points as a .shp file (i.e. a point vector). The Heatmap plug in will then work for you.

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  • They are saved as a shapefile. I may try this plug-in again, but for now the inverted polygon suggestion is sufficient for my purposes. Thank you for the suggestion! – mk24 Mar 21 '16 at 14:39
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If you just need a mask for display, move the country boundary layer to the top and style it using an inverted polygon renderer, see Inverted shading with polygons in QGIS 2.8

  • that's my suggestion too... it works for us! – DPSSpatial Mar 21 '16 at 18:16
  • This was a great suggestion, and it worked perfectly for me. Thanks for answering my question! – mk24 Mar 22 '16 at 20:04

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