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SPATIAL JO
IN
3/1/2
012
Spatial JoinCalculating Number of Physician per Population
GIS in Health and Planning2012 SpringRutgers Universityby Wansoo Im, Ph.D.
Download census tract 2000 fi le
-www.state.nj.us/dep/gis
Download Municipal boundaries
-https://njgin.state.nj.us
“doctor point location layer” (downlaod from Sakai )
Census tract map/Municipali ty boundaries
=>Add Al l Maps in Arc GIS
CENSUS TRACT : OPEN ATTRIBUTE TABLE
In order to see what kind of information it has
DOCTOR LOCATION LAYER : OPEN ATTRIBUTE TABLE
In order to see what kind of information it has
HOW TO JOIN LOCATIONAL DATA WITH DATA FROM ANOTHER LAYER?
Based on the location, we wil l join doctor’s location into Census tract layer.
JOIN DOCTOR POINTS WITH CENSUS DATA LAYER
CLICK “DATA FROM ANOTHER LAYER BASED ON SPATIAL LOCATION”
SELECT “THE LAYER(CENSUS TRACT)” WHICH YOU WANT TO JOIN WITH DOCTOR LOCATION
SET THE DIRECTORY(LOCATION TO SAVE YOUR SHAPEFILE) -> CLICK “SHAPEFILE”
OPEN ATTRIBUTE TABLE TO CHECK IF NEW LAYER(DOCTOR CTR) IS SUCCESSFULLY JOINTBy opening attribute table, you can check if data from 2 original
layers(doctor points/census tract information) are included into a newly-created shapefi les.
LOOK THROUGH DATA
EXCEL – PIVOT TABLE
Objectives :
We are going to export data from maps into dbf.
(dbf. Fi le includes the information of table, therefore, all shapefiles including data in the table have dbf. fi le)
Open dbf. Fi le in Excel
By using Pivot table, we wil l calculate the number of doctors by each census tract
(the number of doctors belonging to each census tract)
OPEN ATTRIBUTE TABLE OF DOC_CTR LAYER
Click the menu icon to export data from table.
EXPORT DATA “DBF. FORMAT FILE”
WHY WE EXPORT DATA FROM TABLE? (DBF. FORMAT)
Originally Doc_CTR shapefi le already has one dbf.f i le, however, i f we start to open it in the excel and modify, we can possibly affect the original map data as the table is directly l inked to a map. Therefore, we would l ike to export data from the original table so as to create new dbf. Fi le(so to speak, “copy” dbf. f i le). In this way, we can adjust data(by using a new dbf. Fi le) in Excel regardless of affecting original data in the map.
OPEN -> CLICK “ALL FILES”-> CLICK “DBF FILE”
OPEN IN EXCEL
WE CAN USE EXCEL FOR DATA CALCULATION!
THE NUMBER OF DOCTORS WITHIN EACH OF CENSUS TRACT. Number of doctors in each of census tract.
How do we calculate?
USE UNIQUE ID TO JOIN “INDIVIDUAL DOCTOR LOCATION” WITHIN CENSUS TRACT
– “KEY” FIELD OR “STFID” (CENSUS TRACT ID)
Why can’t we use Tract f ield? – Tract id is within County (Aggregate scale)
CLICK “INSERT” -> PIVOT TABLE
CLICK “PIVOT TABLE”
CLICK OK
THEN YOU WILL SEE THIS TABLE ;
DRAG “STFID” INTO ROW LABELS
DRAG “STFID” INTO VALUES
COPY THE TABLE
PASTE “VALUE” INTO NEW “SHEET”
Counting Case depending on variable that you chose.
In this case, Fivot Table counts the number of doctors depending on the Census Tract Area(Assigned by unique ID).
CLEAN THE DATA – FIRST ROW SHOULD INDICATE THE NAME OF FIELD
CLEAN THE DATA – DELETE LAST ROW ; TOTAL NUMBER
CHANGE “SHEET” NAME INTO DATA
Name that you can remember
No space/No special characters
(Arc GIS cannot recognize)
SAVE EXCEL FILE AND CLOSE ITBEFORE JOINING IN ARC GIS PROGRAM
CENSUS TRACT LAYER- OPEN ATTRIBUTE BEFORE JOINING DATA
JOIN THE TABLE
JOIN ATTRIBUTE FROM A TABLE
SELECT THE FIELD TO JOIN “STFID” (UNIQUE CENSUS TRACT ID)
CLICK EXCEL FILE YOU SAVED
CLICK THE “SHEET” THAT YOU SAVED NEW DATA (NO.DOCTORS BY CENSUS TRACT)
SELECT THE FIELD(STFID) FROM “DATA SHEET”
CHECK ATTRIBUTE TABLE TO MAKE SURE IF TABLE IS JOINT WELLThere are some null data because this census tract is statewide while
doctor location is located only within Middlesex county.
CALCULATE THE NUMBER OF DOCTORS PER POPULATION WITHIN CENSUS TRACTThe number of doctor
The number of population
Let’s calculate doctors per population.
ADD A NEW FIELD
FIELD CALCULATION
ADD FIELD
10 digit/3decimal
CREATE NEW FIELD (FOR DOCTORS/POPULATION)->RIGHT CLICK TO DO “FIELD CALCULATING”
FIELD CALCULATOR
But you wil l 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 doctors/population*100)
2 WAYS FOR SELECTION
1. Select by Attribute
select the layer “census 2000”, and select the field “population2000” put formula
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.
EX1) SELECTION BY SORTING POPULATION
EX2) SELECTION BY MENU (SELECTING BY ATTRIBUTE)Make sure i f Population(denominator) is 0 not
FIELD CALCULATOR
RATE CALCULATION – WHY 1000? INSTEAD 100?
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 i f there’s doctor, population is over 0)
YOU WILL GET NO.DOCTORS PER POPULATION PERCENTAGE IN NEW FIELD YOU CREATED.
OUTCOME
UNSELECT DATA
GO TO SYMBOLOGY AND MAP IT OUT!
The number of doctors per population
EXPORT MIDDLESEX MUNICIPALITY FROM CENSUS TRACT
SELECT MUNICIPAL OF MIDDLESEX COUNTY
EXPORT MIDDLESEX COUNTY CENSUS TRACT
Field : Double cl ick “County”
Click “Unique value
County= Middlesex county
CHANGE DECIMAL DEGEE IN LEGEND -> CLICK “LABEL” AND “FORMAT LABEL” CHANGE DECIMAL DEGREE.
EXPORT MUNICIPAL BOUNDARY SHAPEFILE.
County = Middle sex
EXPORT MIDDLESEX COUNTY BOUNDARY SHAPEFILE.
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