Arrange data according to geographic regions I have set

Hi everyone,

I have rainfall data across Australia which I am trying to organise into geographic regions.

I have defined the geographic regions on QGIS and have created a shapefile. I then have an array on MATLAB where the rows/columns represent latitude and longitude and the values represents the precipitation data.

I am unsure how to use the shapefile to separate this precipitation data into the regions I created on the shapefile.

Any help would be greatly appreciated thank you!

Answer 1

[KSSV]

1. You can load/ read the shapefile using shaperead.
2. You can seperate the required region from a grid using inpolygon.
3. You can plot the surface using pcolor/ surf.
4. You can use inteprolation using interp2.

Refer this if you want to seperate different regions of shape file from given arrays.

https://in.mathworks.com/matlabcentral/answers/407463-how-to-subset-the-matrix-array-with-shape-file

[Arielle Patapanian]

Hi thanks so much!!! This has really helped. I've managed to apply this with the following code:

xq = latitude
yq = longitude
xv = AER_01.Y
yv = AER_01.X
[in,on] = inpolygon(xq,yq,xv,yv)

However, my AER_01 structure (pictured below) has 781 polygons that I want to constuct, and ideally display whether my latitude and longitude falls within these polygons on one array.

However, when I run the code above, only the first X and Y polygon for AER_01 are tested. Is there a way to make xv and yv represent every X and Y polygon in AER_01?

Thanks so much for any help :)

[KSSV]

You have to run a loop for each polygon.

[Arielle Patapanian]

How do you call upon each polygon in the structure though?

When I try to call upon the first polygon Y value, for example, as below I get an error.

>> AER_01.Y(1)

Expected one output from a curly brace or dot indexing

expression, but there were 781 results.

[KSSV]

S = shaperead(shapefile) ;
N = length(S); 
for i = 1:N
    R = [S(i).X S(i).Y] ;   % this is ith polygon 
end

[Arielle Patapanian]

Thank you so much!!! Absolute life saver :D