How can I remove the black pixels on the shapefile below?

I have never seen this before after receiving a shapefile and categorizing it. This shapefile shows percentage of flooded area per municipality. I'm displaying polygons here (municipalities) but I can't get rid of the black pixels. Are they no data values?

black artifacts on map

closed as off-topic by underdark Dec 10 '17 at 19:22

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This problem cannot or can no longer be reproduced. Changes to the system or to the asker's circumstances may have rendered the question obsolete, or the question does not include a procedure to enable potential answerers to reproduce the same symptoms. Such questions are off-topic as they are unlikely to help future readers, but editing them to include more details can lead to re-opening." – underdark
If this question can be reworded to fit the rules in the help center, please edit the question.

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    I can't follow the logic why this is closed, can someone explain why this is off-topic? @underdark – Matthias Kuhn Dec 10 '17 at 23:09
  • @MatthiasKuhn I chose "cannot be reproduced" since the the issue has nothing to do with no value pixels. I don't think the question has future value as it stands. Feel free to reopen if you think otherwise. – underdark Dec 11 '17 at 20:15
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    I think that's lack of knowledge about taxonomy while the issue itself is something others have run into as well. I'll reopen with the term "artifacts" instead of "no value". – Matthias Kuhn Dec 12 '17 at 7:16
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    My first thought was also that what's showing is an artifact (i.e. a black symbol outline). On-topic and reproducible. – Alex Hajnal Dec 12 '17 at 7:55

The symbol most likely has a black outline. Go to the style configuration of the layer and set the stroke color to Transparent.

No data value is a term normally used with respect to raster data, while with vector data (like shapefiles) normally the term to use is NULL value for an attribute, but that's not related to anything that's going on here.

  • that's exactly it! I feel embarrased.... Thank you very much Matthias! – 39ace39 Dec 10 '17 at 14:19

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