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Hot Spot Analysis: Create a custom bar graph
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This bar graph looks like histogram, but it is oriented horizontally instead of vertically.
This bar graph looks like a histogram of the data; though it is oriented horizontally instead of vertically. This orientation allows the graphic to be directly associated with the color ramp legend which is displayed next to it.

What: The horizontal bar chart on this poster shows the distribution of 911 calls and uses the same colors as on the maps. The orientation of the graphic has been changed from the default vertical to horizontal. The graph was created and customized to allow it to be visually and physically associated with the color ramp legend for the raster data. Another topic explains how to create this custom legend.

Why: Clear graphic association is desirable when you want your readers to note the relations between elements on the page. This poster required a modification to the orientation of the bar graphic which acts as a histogram to show the data distribution.

How: We created a bar chart and customized it. In order to do this we first ahd to craete a table that summarized the 911 call data. This was necessary because summarized data provided counts for each of the bars in the graph. We customized the graph so it could quickly be visually related to the legend next to it. Here are the steps we followed:

  1. The map was symbolized using the HSCLass field in our call data. We added this field and set its values to range from one through five. The values for one through fivc were assigned as follows:
    • 1 = Extreme significant cold spots
    • 2 = Significant cold spots
    • 3 = Not significantly hot or cold
    • 4 = Significant hot spots
    • 5 = Extreme significant hot spots
    We manually calculated these values based on querying the data for each range of values in this classification. To make a histogram of that data distribution, we summarized the data on the HSClass field and specified that the Count_# field be summed, which produced a summary table.
  2. Summary table used to create this graph
    Here is what the summary table looks like.
  3. Here is how we made the graph:
    1. Make sure the data frame you added the summary table to is active (in the table of contents, the name of the active data frame is in a bold font). Then from the Tools menu select Graphs, and then Create.
    2. Set the Graph Type to Horizontal Bar.
    3. Set the Layer/Table to the summary table.
    4. Set the Value Field to the field that contains data values of interest (F2 for our map).
    5. Uncheck the Add to Legend check box, because the graph does not need to have a legend.
    6. Click the Appearance tab and change the Title to a concise and clear description of the graph.
    7. Check the results in the 3D view box.
    8. Click OK to close the properties window.
  4. We also needed to set some advanced properties in order to finish the graph:
    1. Right click on the graph’s window and select Advanced Properties from the menu.
    2. Click on Chart in the left side of the window, expand Axis, and select Bottom Axis.
    3. On the Scale tab, change the Increment to 50.
    4. On the Title tab, change the title to "Total calls in each bar".
    5. We also needed to change the colors in the graph to match the colors from our graduated point symbol layer. In the Advanced Graph properties (the window is named Editing) click on "Data" node in the tree view on the left side of the window to display the data. Click on the multi-colored button at the lower right to display the colors that are used for each bar. Double click each color to change it to what was used in the map. This uses the windows color palette, so before we started, we wrote down the RGB values for each of the colors that our layer used, and then typed them in as we went along assigning the colors.
    6. Editing the Data properties allows you to change the colors in a bar graph.
      Editing the Data properties allows you to change the colors in a bar graph.
  5. Now that you have made all your edits, you are ready to add the graph to the layout. Right click on the graph and select Copy as Graphic. Then in the layout, right click and select Paste. (The reason to do this is due to a bug in the graph which does not save the colors you just set. Copying the graph as a graphic lets you preserve your work. If you add the graph to the layout, it will look like everything is working, but when you close your map document and open it again, the colors will be lost.)
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