Using if and of two columns to find the value in another column

I have a shape file. I cannot attach it since it is too large.

But I used the code to read as:

S = shaperead('conus_20160101_24h.grb-var0.shp')

Now, I am able to get my table.

There are five columns: "Fields", "Geometry", "X", "Y", "value", "datetime"

What I need is to find "value" based on "X" and "Y"

For instance, if X is between 78 and 79 and Y is between, 48 and 49, read the value in "Value".

Thanks,

J

Answer 1

[Matt J]

Here, I use T as the name of your table,

lookup=abs(T.X-78.5)<=0.5 & abs(T.Y-48.5)<=0.5;

T.Value(lookup),

[Joe Sheckles]

Thanks but I get this response:

Error using -

Too many input arguments.

Error in ReadStageIV (line 2)

lookup=abs(S.X-73.9668)<=0.00005 & abs(S.Y-40.7995)<=0.00005;

[Matt J]

I suggest attaching S in a .mat file so that we can work with it. I suspect, however, that it is not a table variable.

[Joe Sheckles]

Okay. Let's see. Maybe I'll provide a little background. Overall, I am trying to find a precipitation value ("Value") for a longitude (X) latitude (Y) coordinate. And I have shape files for each day of the year for 2016.

When I input:

R1 = shaperead('conus_20160101_24h.grb-var0.shp')

A table, titled R1, appears in the work space. It says it is a "582,653x1 struct"

When I click on the table, a pop-out table appears with the values. I've copied the first five rows values on an excel sheet (attached).

So lets say I want to read the precipitation value of when X = -106.383 and Y = 26.623

How would I code that?

(I've also attached the matlab file)

Thanks,

J

[Matt J]

Attach R1 in a .mat file so we can study what it contains. If R1 is too big to upload, then just attach a part of it.

Rsection=R1(1:10);
save attachment Rsection

Also, for clarity's sake, be mindful that a "table" in Matlab refers to a very specific type of variable:

https://www.mathworks.com/help/matlab/tables.html

A struct is also a very specific variable type, so if R1 is a struct, it is not a table.

https://www.mathworks.com/help/matlab/ref/struct.html

[Joe Sheckles]

I could not attach the R-sections - too large - even when compressed or doing 1:2.

I'm attaching a link. It also has the shapefile, m., mat.

https://drive.google.com/open?id=1WO92wbZ3Xn1Kz02KIEU1zJ27JGCqxe5p

Hope this works.

Thanks

[Matt J]

So, one solution would be to convert R1 to a table, and then use the steps I originally proposed, e.g.,

 S=struct2table(R1);
 S.X=-S.X;  %for some reason all X were negative
 
 lookup=abs(S.X-73.9668)<=1 & abs(S.Y-40.7995)<=1;
 
 values = S.value(lookup);

[Joe Sheckles]

Yes. This works perfectly. Thanks!