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Step 13: Spatial Analysis V: Working with Charts

Charts That Stand Alone

Suppose that you are examining the impact of different pest-control strategies--IPM strategy number 1, IPM strategy number 2, using no pesticides, applying Malathion, and applying Diazinon. We want to produce a chart to illustrate the impact of these strategies on the pest populations over three different time periods.

To do so, we need to work with the attributes tables that are in our GIS program. From these tables, we will create bar-charts to help compare the relative effectiveness of the five strategies over the three time periods.

This theme has information on the five different pest-control strategies. The map of this theme covers the same area as that in the theme "Shambas.shp." We have combined the parcels in "Shambas.shp" into five different groups, each group experimenting with a different pest-control strategy.

Change the name of this theme in the Table of Contents to "Pest Control Strategies." (Use the Theme Properties dialog box to change the name.)

Click on the Open Theme Table button located at the top of the screen below the menu.

The table "Attributes of Pest Control Strategies" now appears. Notice that there are five rows of data in the table, one for each pest-control strategy.

In the first time period, "Numpest1," which represents conditions before any pest-control strategies were used, the number of pests was uniform throughout the area. Thus, in the table for our new theme, "Pest Control Strategies," the number of pests for each strategy in the first time period is listed as 100. The pest counts, however, varied significantly among the strategies during the second ("Numpest2") and third ("Numpest3") time periods.

Now click on the chart button at the top of the screen below the menu.

The Chart Properties dialog box now appears.

Let us examine the dialog box. At the top is a small box with the "Name" of our chart, "Chart 1." Here you can type in a new title for the chart. Type in the phrase "Impact of Pest Controls Over Time."

Just below the "Name" of the chart is the "Table" whose data we will be using to create our new chart; in this case, we are using data from "pest-strategy.dbf".

Below on the left is the category "Fields," which contains a list of the fields in our table. In the middle are two buttons whose labels are dimmed because they are not active yet. On the right is the category "Groups" with an empty box below it. The basic idea is to select the fields that we want in our chart and add them to the box under the category "Groups."

Click on the field name "Numpest1" on the left under the heading "Fields" and notice that the button labelled Add is no longer dimmed, which means that we can now use it.

Click on the Add button. Now the field "Numpest1" is added in the box on the right under "Groups."

Now add the fields "Numpest2" and "Numpest3" to the box under "Groups" in the same way.

Now look at the small box below the category "Fields" with the heading "Label series using:". In its drop-down list (which now lists "None") select the field "Strategy" (which contains information about the types of pest-control strategies). This will enable us to label the chart with the names of the pest-control strategies.

The field "Strategy" now appears in the small box below the heading "Label series using."

Click the OK button at the top right in the dialog box and a bar chart appears.

(Note: if you cannot see all the labels in the chart clearly, put your cursor in the corner of the border around the chart and drag the corner out to enlarge the chart.)

Right now we have the labels for the number of pests in the different time periods in the X axis and the pest-control strategies listed in the chart's legend. By default, ArcView places in the chart's legend the categories from the field chosen for "Label series using" in the Chart Properties dialog box. However, in this case it is more effective visually to reverse them, so click on the Series from Records/Fields button.

We can now see clearly the effectiveness of the different strategies over time, with IPM2 being the most effective.

Note that there are other types of charts that we could create as well, as indicated by the buttons at the top of the screen below the menu.

Which style of chart is most useful in illustrating your data depends on the types of data that you are examining.

We also should add a title to our chart. Click on the Chart Element Properties button in the second row of buttons at the top of the screen.

Then click on the word "Title" above the five bar charts. This brings up the Chart Title Properties box.

Type in for the title "Impact of Pest Control Strategies" where the word "Title" is highlighted in black.

(Note: You can also change the location of the title in the chart by clicking in the Chart Title Properties box where you want the title to be placed.)

The title now appears above the charts.

You can also change the appearance of the legend, X axis, and Y axis. Make sure that the "Chart Element Properties" button is depressed and click once on any element in the chart that you want to change. Make the changes in the dialog boxes that appear.

In addition, you can also create charts of aggregated data in tables produced when you use the Summarize tool that we used in the previous Step.

We will now create a chart of the summary table ("total-acres.dbf") that we produced of total areas (in acres) devoted to the four main crops in the theme "Shambas.shp."

Close our chart and close the table "Attributes of Pest Control Strategies."

We want to open our table "total-acres.dbf".

Click on the Open button and our summary table appears.

Create a bar chart of this table. In the Chart Properties dialog box, highlight "Sum_Acres" in the category "Fields" and click on the Add button so that "Sum_Acres" appears under the category "Groups." For the category "Label series using" select "Maincrops" from the drop-down list. Make the title of the bar chart "Acres in Main Crops." Your chart should look like this:

You can delete the X axis label "Sum_Acres," which is not needed in the chart. Click on the Chart Element Properties button in the second row of buttons at the top of the screen.

Then click on the X-axis title "Sum_Acres" in the chart and the Chart Axis Properties dialog box appears.

In the section "Group labels" delete "Sum_Acres" and click on the OK button. Your chart should look like this:

We have now learned how to produce charts in ArcView.

Adding Charts to Layouts

Close the chart "Acres in Main Crops" and close the table "total-acres.dbf".

Select "Impact of Pest Controls Over Time" and click on the Open Button. The reason that we have done this is because in order to insert a chart into a Layout, the chart has to be open.

We want to return to our "View1," which has our map of pest-control strategies, but do not close the chart "Impact of Pest Controls Over Time." Leave it open. To also open our View1, shift again to the Project Window. (Go to the menu at the top of the screen and select Window and then Uganda.apr from the drop-down list.)

Select "View1" and click on the Open Button.

We now have our map of pest-control strategies.

Create a Layout of our map (See Step 8). When the View - Layout window appears, select "<New Layout>". In the Layout, change the title from "View1" to "Pest Control Strategies." Move the title to the left to make room for the chart.

Note that in this Layout the scale bar units at the bottom are in "miles." If your scale bar units are in miles, you should change them to "meters". (If they are in meters, do not change the scale bar.)

To change the scale bar units to "meters," click on the pointer button , which is the first button on the left in the second row of buttons at the top of the screen.

In the section "Units," select from the drop-down list "meters." Click on the OK button.

The distance units in the Layout are now set to "meters."

This action brings up a drop-down list of framing tool icons.

The framing tools enable you to add various ArcView elements to a Layout.

Select the Chart Frame tool that looks somewhat like a chart.

Note that cross-hairs have appeared on your cursor when you move it over the Layout. Outline the area on your Layout where you want to place the chart by dragging your cursor to create a rectangle.

Release your mouse button. The Chart Frame Properties dialog box now appears.

In the section to the right of "Charts" click on the chart name ("Impact of Pest Controls") you want to incorporate into the Layout and then click on the OK button. The chart appears in the Layout in the area you defined with your cursor.

Select the pointer button at the far left in the second row of buttons at the top of the screen. Then, click once near the corner of the Layout and the handle bars around the inserted chart will disappear.

Our Layout is somewhat crowded in this case. We could reposition and resize the other elements using the pointer tool.

We have now learned how to insert a chart into a Layout.

Incorporating Charts into Maps

We can also produce the same bar charts (and pie charts) so that they appear within our map.

In our View1, make sure that "Pest Control Strategies" is still active.

The Legend Editor dialog box should look like this.

On the left side of the dialog box is a list under the heading "Fields." We need to select the fields that we want in our chart and shift them to the right side of the dialog box under the heading "Fields."

Then click on the Add button in the middle of the dialog box so that the three fields with their new color symbols appear on the right side of the dialog box under the heading "Fields."

(Note: If you do not like one of the colors, you can change it by double-clicking on it and using the color palette window to change it.)

Before applying the changes to our map, note that in the bottom left of the dialog box under "Chart Type" there are symbols for pie charts and bar charts. We want to produce a bar chart, so click on the symbol for bar charts to select it. (If selected, it will be pressed in, as in the above image.)

Now click on the Apply button in the bottom right of the dialog box and close the dialog box.

A problem has developed. Because we are displaying the charts in the theme "Pest Control Strategies," the original colors that we had on the map previously to display the spatial distribution of the pest-control strategies has now disappeared, being replaced by a single background color.

There are two strategies to solve the problem.

One solution that we can implement now is based on the lessons that we have learned. Double-click on the theme name "Pest Control Strategies" to bring up the Legend Editor dialog box again and notice that at the bottom of the dialog box there is a small box beneath the category "Background Symbol".

This box has the current background color that is on our map. Double-click on the box to enable us to change the fill pattern to a clear one.

This brings up the Fill Palette window. Click on the top left box in the Fill Palette window, which is for a clear fill pattern.

Close the Fill Palette window, click on the Apply button in the Legend Editor dialog box, and close the Legend Editor dialog box

We can add another copy of our original theme "Pest Control Strategies" to the Table of Contents. This copy will also show the bar charts and have a clear fill pattern.

Make sure "Pest Control Strategies" is active.

Select from the menu at the top of the screen Edit and then Copy Themes from the drop-down list.

Then select from the menu at the top of the screen Edit and then Paste from the drop-down list.

A copy of our theme appears at the top of the Table of Contents.

Change the second, original theme "Pest Control Strategies" in the Table of Contents back to a map with a unique value legend type using the field "Strategy".

We can now see clearly on our map how the numbers of pests have changed over time in response to the different types of pest-control strategies. The benefits of IPM2 strategy are clearly illustrated.

A second solution would be to add another theme represented by points. In this theme, one point would be located on top of each polygon in the theme "Pest Control Strategies". Each point would have associated with it the data on the number of pests in the three different time periods in its attributes table. We could then use the point theme to display the charts; in such cases, the charts would be drawn directly on top of the points.

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