Dear community! 

I’m new to QGIS and hope you can follow my process and my question. Would be 
more than happy to get your help! 

So I have a raster layer with a cumulative value for each raster giving 
information about land modification (in 2016) 

I have another vector layer with points providing information where an outbreak 
of a zoonotic infectious disease occurred (in 2016) 

I want to examine the effect / association between  land modification and 
outbreak (I´ll do this with a binary logistic regression analysis in SPSS) 
therefore I want to generate a text file with values of the land modification 
for the location of the outbreak - I’ve done this with the tool "point 
sampling“. 

But I also need values of land modification located at the points 
„no-outbreaks“. (to calculate the binary logistic regression analysis later in 
SPSS) Therefore I’ve generated random points. However, these points are truly 
random :) 
So most random point „lay in the ocean“ and therefore I don’t get values of 
land modification. 

So my question: How do I deal with that? Can I give a kind of command that all 
random points have to lie on land? and to give a certain radius for the „not 
random“ points - outbreaks. 

someone said I can do this via raster calculator. But I cannot follow it, since 
I don’t calculate two raster layers?! I gave me this kinda command to deal with 
my issue: (via raster calculator?!) 

L = grid cell is on land 

B = Buffer around outbreaks with radius r (tbd: minimum distance between 
outbreaks and random non-outbreaks) 

D = L / B (difference  "L without B „ = country on which a random non-outbreak 
can lay) 


Thank you so much!!!!!!!

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