SP Spatial Join
Calculating Number of Physician per Population
2 GIS in Health and Planning
1/ 2012 Spring
3/ Rutgers University
by Wansoo Im, Ph.D.
Download census tract 2000 file
Download Municipal boundaries
“doctor point location layer” (downlaod from Sakai )
Census tract map/Municipality boundaries
=>Add All Maps in Arc GIS
CENSUS TRACT : OPEN ATTRIBUTE TABLE
In order to see what kind of information it has
OPEN ATTRIBUTE TABLE TO CHECK IF NEW
LAYER(DOCTOR CTR) IS SUCCESSFULLY JOINT
By opening attribute table, you can check if data from 2 original
layers(doctor points/census tract information) are included into a
EXCEL – PIVOT TABLE
We are going to export data from maps into dbf.
(dbf. File includes the information of table, therefore, all shapefiles
including data in the table have dbf. file)
Open dbf. File in Excel
By using Pivot table, we will calculate the number of doctors by each
(the number of doctors belonging to each census tract)
WHY WE EXPORT DATA FROM TABLE?
Originally Doc_CTR shapefile already has one dbf.file, however, if we
start to open it in the excel and modify, we can possibly affect the
original map data as the table is directly linked to a map.
Therefore, we would like to export data from the original table so as
to create new dbf. File(so to speak, “copy” dbf. file). In this way, we
can adjust data(by using a new dbf. File) in Excel regardless of
affecting original data in the map.
But you will have 0 if denominator(total population2000=0) is 0
Select the data which population 2000 is more than 0
Use Field Calculator to use formula (number of
2 WAYS FOR SELECTION
1. Select by Attribute
select the layer “census 2000”, and select the field “population2000”
Pop2000>0 ->click apply
2. Sorting Ascending in Attribute Table
Open Attribute table, sort the data regarding population 2000, and
select data which is more than 0 in population 2000 field.
IF THERE’S NULL DATA => ERROR!!!
Population should be over 0 AND
Number of doctors shouldn’t be null data
Therefore, number of doctor is more than 0 and calculate it again
(Assume that if there’s doctor, population is over 0)
YOU WILL GET NO.DOCTORS PER POPULATION
PERCENTAGE IN NEW FIELD YOU CREATED.