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If you saw the JMP 9 launch webcast on Oct. 12 or have seen the JMP website lately, you know geographic visualization is a prominent feature of JMP 9. You likely saw a map being drawn underneath the data, and you may have wondered, "How did they do that?" The answer is background maps.
Background maps are a new feature in JMP 9. There are different types of background maps. Some maps are built into JMP, delivered as part of the JMP install. Other maps are retrieved from an Internet source, and still other maps are user-defined. From a user’s perspective, adding a background map may require nothing more than flipping a switch. That switch will generate a great-looking map, giving your data a geographic context and giving you a whole new way to view your data.
Since background maps are new, let’s take a quick look at the overall functionality. The best way to do this might be to look at the Background Map dialog, which is available from the graph right-click menu next to Background Color.
The Background Map dialog shows two columns of choices. The column on the left is called Images. The column on the right is called Boundaries.
The boundary-style maps are vector-based shapes. This type of map draws an outline around a defined area. Some of these are provided as part of JMP, or a user can define his or her own. Because of this, the list you see may be different than the one presented here. This type of background map has been mentioned in other blog posts, such as What Factors Affect Office Temperature? Creating Custom Maps.
The image maps are raster images. These are more like the type of map you see when you open an atlas or use a GPS. There are two types of image-based background maps. Simple Earth and Detailed Earth are tiles of images that live locally on your computer. They were installed as part of JMP. The NASA server and Web Map Service options are Internet-based mapping options. By the way, you can turn on both an image map and a boundary map at the same time.
When you turn on a background map for a graph, the axes are used to display the appropriate portion of a map. The Earth is defined as -180° to 180° in the horizontal direction (longitude), going from left to right. It is defined as 90° to -90° in the vertical direction (latitude), going from top to bottom. The limits of the axes will be used to define the limits of the map that get displayed.
Let’s experiment with the background map options. To do so, simply open a JMP data table that has geographical-based data. You can find some of these in the Samples Data directory that is installed with JMP. Run JMP and open the sample data file called Hurricanes.jmp. Run the script called Bubble Plot (not the script called Bubble Plot with Map, as that would be jumping ahead). When you run this script, you get a graph that looks like this:
This graph shows the location of a hurricane, Claudette, on July 15th, 1979. The first thing you might see is that even though the location of the hurricane is plotted, it doesn’t really tell us where it is. We need a little more context. We could look at the axes, but I would bet that not too many people would know exactly where 10° North latitude, 50° West longitude would put us on the Earth. Being incredibly brilliant and logical, you might realize that because it is a hurricane, it is likely to be over the Atlantic Ocean. Of course, you would be correct, a true testament to your intellect. But we still don’t know where it is, really. Is it out over the middle of the Atlantic, or is it over a small island? This could make a big difference, especially for the inhabitants of the small island. Obviously, a map in the background of our graph would add a good deal of information. So let’s right-mouse-click over the graph, and we’ll get a context-sensitive menu.
Select Background Map… and you will be presented with the Background Map dialog, which we discussed earlier. You can now select what type of background map you would like to see. Experiment with the different options and see what you get. Use the Go button to see an animation of the hurricane data, moving over the background map. Adjust the axes or use the zoom tool to change what part of the world you are viewing. You will see the map adjust as the view does. Tip: You can always right-mouse-click over the graph and select Size/Scale->Size to Isometric to get the aspect ratio of your graph to be proportional again.
Here is what you will get if you select Simple Earth as the background map:
Watch for future blog posts, where I will discuss the different types of maps in greater detail. But for now, I hope you’ll take this chance to explore them for yourself. If you do, please let me know what you think. Your suggestions might even make it into my future work.