Extract matrix subset based on latitude and longitude

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Janet Reimer
Janet Reimer 2016-10-24
编辑： Kirby Fears 2016-10-24
I have a matrix of data and want to extract various subsets (0.5 degree grids) based on latitude and longitude. My file is not one that I downloaded from NASA, ect...
I have been trying to use "find" where latitude and longitude are columns 1 & 2 of the matrix "all_time":
x=all_time(:,3:15);% tem=find(all_time(:,1)<27.5 & all_time(:,1)>28.0 & all_time(:,2)<-79 & all_time(:,2)>-78.5); box1=x(tem);
I am trying to extract boxes of 0.5 by 0.5 degrees for all the variables in columns 3 to 15 of the matrix. My box1 is an empty matrix.
Thanks

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回答（1 个）

Kirby Fears
Kirby Fears 2016-10-24
编辑：Kirby Fears 2016-10-24
Janet,
These conditions are contradictory:
all_time(:,1)<27.5 & all_time(:,1)>28.0
None of your values could be below 27.5 and above 28 at the same time. I suppose you meant to flip those comparators as:
all_time(:,1)>27.5 & all_time(:,1)<28.0
Also, tem will contain the rows satisfying your longitude and latitude conditions. If you'd like to extract all columns of x corresponding to those rows, you'd index like this:
box1=x(tem,:);
Hope this helps.
  2 个评论
Janet Reimer
Janet Reimer 2016-10-24
Yes, thank you, I had inadvertently flipped the signs, but "box1" is still empty.
Kirby Fears
Kirby Fears 2016-10-24
编辑：Kirby Fears 2016-10-24
Are you sure you have data in that matrix meeting all conditions? You can try removing one condition at a time to see which one is causing a problem. You might need to use a >= or <= sign.

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