Exercise 6 – Summarizing data and making field calculations in ArcMap

In the first part of this exercise you learn how to summarize the data and make field calculations in ArcMap. You will use PAMCH.SHP shapefile. You will take a look at number of low birth weight data in Pennsylvania Counties. You will open the attribute table for PAMCH.SHP and take a look at the statistics of some of the fields to familiarize you with the dataset. You will use the “Field calculator” to perform a variety of calculations.

1.  Start ArcMap if you haven’t already. Add PAMCH.shp

2.  Right Click on the PAMCH layer à Open Attribute Table. Scroll to the right and examine the fields in the table. A portion of the right side of the table is reproduced below. Note the field names: LBW90 (# of LBW in 1990); BIRTH90 (# of births in 1990); LBW91 (# of LBW in 1991); BIRTH91 (# of births in 1991); LBW92 (number of births in 1992). Close the table.

3.  Right Click on the LBW90 field à Statistics

Take a look at the information in the Statistics of PAMCH window below. It shows the count (number of counties) the minimum and maximum number of low birth weight babies, sum, mean and standard deviation. In addition a histogram of frequency distribution of LBW appears to the right. The drop box for Field can be used to select different fields in the attribute table. Try it now.

Next we will aggregate low birth weights and births for 1990, 1991 & 1992 and then add the LBW’s and Births over the three years. This aggregated data will then be used to calculate LBW rate.

4.  Right Click on PAMCH à Open Attribute Table. Click on the Options Button à Add Field…

5.  In the Add Field Dialog Box, Type the following and then Click OK. A field with the name LBWR_90_92 will be added to the end of the attribute table.

6.  In order to edit your table and go back and correct mistakes, you should make the attribute table editable. Go to View à Toolbar à Editor. This will open the Editor Toolbar.

7.  On the Editor Toolbar, Select Start Editing from the Editor drop-down.

Then Click on PAMCH to select it and Click the Start Editing Button

8.  Right Click on the field LBW_90_92 in the attribute table and Select Calculate Values…

In the Field Calculator Dialog Type: (([LBW90] + [LBW91] + [LBW92])/( [BIRTH90] + [BIRTH91] + [BIRTH92]) )*100

Then Click OK Button

LBWR_90_92 will be calculated as shown:

9.  Right Click on PAMCH à Properties

1. Select Symbology Tab

2. Quantities à Graduated colors

3. From Value: drop-down box Select LBW_90_92

4. Click OK

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