- Use the gridmaker.ave script (located in the samples directory)
to create a grid over the state. Make this script the "apply"
action on a new button in the view. You get to this by double-clicking
the toolbar, then selecting tool from the dropdown menu. (I'll
show you in class).
-
Use the Theme-> Select by Theme function
to do a spatial query of all grids that intersect the state
(assuming that you drew your box larger than the state).
Save this as a new theme. We won't worry about the boundary
problem.
-
Open the Table for this new theme, open the
table for the earthquakes theme and do a spatial join by
clicking on the Shape field in each table and clicking the
join button.
-
Click on the field Label and choose Summarize
from the Field menu. Accept the defaults in the dialog box.
This gives you a table of how many earthquakes occured
in each grid cell.
-
Now join the summarized table back to your
grid table so that you will have a list of all the grid
cells and how many earthquakes are in each. Now you can
plot a graduated color map of earthquake occurence, which
will be less busy visually than plotting all of the earthquakes.
Cool, huh? Summarize this table in the same way that you
did in step 3, but this time summarize on the field Count.
-
Export the summarized table to DBF so that
you can import it to Excel.
-
Download my Poisson
example spreadsheet. For a quadrat analysis you need
to have at least 5 events in a category. You will probably
combine all of the categories above a certain value. For
my 50 x 50 example I combined everything above 5. Remember
that the sum of all probabilities in the Poisson distribution
is 1. I'll cover the details in class.
-
Alter the spreadsheet to accomodate the grid
size that you used. Your Chi Square value should be pretty
large, since this is obviously a clustered data set!