Because we want the image to contain no borders, we must initialize the figure window to contain only the figure axis. Note that the figure must be created with the correct aspect ratio, or the image will contain borders. We will use a constant width of 5 inches and find the correct height by multiplying the aspect ratio of the input data the number of rows divided by the number of columns of the variable. This should have created an empty figure window.
We are now able to generate image using the imshow command. Note that imshow draws the figure from top to bottom like an image so we must flip the data vertically using flipud prior to displaying. Also, we want to visualize the data on a log color scale, so we will take the logarithm of the data log 0 will show up as white in the figure. Finally, we will turn off the axis to remove any remnants of tick marks from the display axis, and save the file to a png image named Infected.
External images can be included into Google Earth in a number of different ways. What we are interested in is displaying our image over the ground. This is what is known as a GroundOverlay. By default these methods assign the first three bands to red, green and blue, respectively. The default stretch is based on the type of data in the bands e.
To achieve desired visualization effects, you can provide visualization parameters:. The following illustrates the use of parameters to style a Landsat 8 image as a false-color composite:. In this example, band 'B5' is assigned to red, 'B4' is assigned to green, and 'B3' is assigned to blue. To display a single band of an image in color, set the palette parameter with a color ramp represented by a list of CSS-style color strings.
See this reference for more information. In this example, note that the min and max parameters indicate the range of pixel values to which the palette should be applied.
Intermediate values are linearly stretched. Also note that the show parameter is set to false in the Code Editor example. This results in the visibility of the layer being off when it is added to the map. It can always be turned on again using the Layer Manager in the upper right corner of the Code Editor map. You can use image. Pixels equal to zero in the mask are excluded from computations and the opacity is set to 0 for display. Use the image.
For example, to convert the false-color composite and NDWI to 3-band display images, use:. You can use masking and imageCollection. The mosaic method renders layers in the output image according to their order in the input collection. The following example uses mosaic to combine the masked NDWI and the false color composite and obtain a new visualization:.
Example : If you have a table with 10 rows, and you call setRows [2,7,1,7,9] , and then hideRows [7,9] , the rows in the view will then be [2,1]. Specifies which columns are visible in this view. Any columns not specified will be hidden. If you don't call this method, the default is to show all columns. The array can also contain duplicates, to show the same column multiple times. Columns will be shown in the order specified.
This is a convenience syntax for setRows rowIndexes below. For example, setRows 5, 10 is equivalent to setRows [5, 6, 7, 8, 9, 10]. The array specifies the order in which to show the rows, and rows can be duplicated. Note that only the rows specified in rowIndexes will be shown; this method clears all other rows from the view. The array can also contain duplicates, effectively duplicating the specified row in this view for example, setRows [3, 4, 3, 2] will cause row 3 to appear twice in this view.
You can use getFilteredRows or getSortedRows to generate input for this method. A ChartWrapper class is used to wrap your chart and handle all loading, drawing, and Datasource querying for your chart. The class exposes convenience methods for setting values on the chart and drawing it. This class simplifies reading from a data source, because you do not have to create a query callback handler. You can also use it to save a chart easily for reuse.
Another bonus of using ChartWrapper is that you can reduce the number of library loads by using dynamic loading. Additionally, you don't need to load the packages explicitly since ChartWrapper will handle looking up and loading the chart packages for you.
See the examples below for details. However, ChartWrapper currently only propagates a subset of events thrown by charts: select, ready, and error. Other events are not transmitted through the ChartWrapper instance; to get other events, you must call getChart and subscribe to events directly on the chart handle, as shown here:.
Draws the chart. You must call this method after any changes that you make to the chart or data to show the changes. If this chart gets its data from a locally-defined DataTable , will return a reference to the chart's DataTable. If this chart gets its data from a data source, it will return null. Any changes that you make to the returned object will be reflected by the chart the next time you call ChartWrapper.
The ChartWrapper object throws the following events. Note that you must call ChartWrapper. The following two snippets create an equivalent line chart. The first example uses JSON literal notation to define the chart; the second uses ChartWrapper methods to set these values.
The ChartEditor class is used to open an in-page dialog box that enables a user to customize a visualization on the fly. Opens the chart editor as an embedded dialog box on the page. The function returns immediately; it does not wait for the dialog to be closed. If you do not lose scope of the instance, you can call openDialog again to reopen the dialog, although you must pass in a ChartWrapper object again.
The chart must either have a populated DataTable , or be connected to a valid data source. Use this to enable the user to specify a data source for the chart. This property can be one of two values:. The following example code opens a chart editor dialog with a populated line chart. The google. Note that this does not modify the input DataTable.
The returned table includes one row for each combination of values in the specified key columns. Each row includes the key columns, plus one column with an aggregated column value over all rows that match the key combination for example, a sum or count of all values in the specified column. Instructions on how to define your own aggregator are given after the method description. A DataTable with one column for each column listed in keys and one column for each column listed in columns.
The table is sorted by key rows, from left to right. The API provides the following modifier functions that you can pass into the keys. The API provides the following aggregation functions that you can pass into the columns. You can create a modifier function to perform a simple transformation onkey values before the group function groups your rows. This function takes a single cell value, performs an action on it for example, adds 1 to the value , and returns it.
The input and return types need not be the same type, but the caller must know the input and output types. Here's an example of a function that accepts a date and returns the quarter:. You can create an aggregation function that accepts a set of column values in a row group and returns a single number: for example, returning a count or average of values.
Here is an implementation of the provided count aggregation function, which returns a count of how many rows are in the row group:.
You specify one or more column pairs key columns between the two tables, and the output table includes the rows according to a join method that you specify: only rows where both keys match; all rows from one table; or all rows from both tables, whether or not the keys match.
The results table includes only the key columns, plus any additional columns that you specify. Note that dt2 cannot have duplicate keys, but dt1 can. The term "key" means the combination of all key column values, not a specific key column value; so if a row has cell values A B C and columns 0 and 1 are key columns, then the key for that row is AB.
A DataTable with the key columns, dt1Columns , and dt2Columns. This table is sorted by the key columns, from left to right. When joinMethod is 'inner', all key cells should be populated. For other join methods, if no matching key is found, the table will have a null for any unmatched key cells.
The Google Visualization API provides formatters that can be used to reformat data in a visualization. These formatters change the formatted value of the specified column in all rows. Note that: Formatters modify only the formatted values, not the underlying values.
Formatters only affect one column at a time; to reformat multiple columns, apply a formatter to each column that you want to change. If you also use user-defined formatters, certain Google Visualization formatters will override all user-defined formatters. The actual formatting applied to the data is derived from the locale the API has been loaded with. For more details, see loading charts with a specific locale.
Here is an example of changing the formatted date values of a date column to use a long date format "January 1, " :. Adds an up or down arrow to a numeric cell, depending on whether the value is above or below a specified base value. If equal to the base value, no arrow is shown. ArrowFormat supports the following options, passed in to the constructor:. A number indicating the base value, used to compare against the cell value.
If the cell value is higher, the cell will include a green up arrow; if the cell value is lower, it will include a red down arrow; if the same, no arrow. Adds a colored bar to a numeric cell indicating whether the cell value is above or below a specified base value.
BarFormat supports the following options, passed in to the constructor:. Assigns colors to the foreground or background of a numeric cell, depending on the cell value. This formatter is an unusual, in that it doesn't take its options in the constructor. Instead, you should call addRange or addGradientRange as many times as you want, to add color ranges, before calling format.
Colors can be specified in any acceptable HTML format, for example "black", " ", or " ". Any cell with a value in the specified from — to range will be assigned color and bgcolor. It is important to realize that the range is non-inclusive, because creating a range from 1—1, and a second from 1,— 2, will not cover the value 1,! Assigns a background color from a range, according to the cell value. The color is scaled to match the cell's value within a range from a lower boundary color to an upper boundary color.
Note that this method cannot compare string values, as addRange can. Tip : Color ranges are often hard for viewers to gauge accurately; the simplest and easiest to read range is from a fully saturated color to white e. DateFormat supports the following options, passed in to the constructor:. A quick formatting option for the date.
The following string values are supported, reformatting the date February 28, as shown:. You cannot specify both formatType and pattern. A custom format pattern to apply to the value, similar to the ICU date and time format.
You can read more details about patterns in the next section. Returns the formatted value of a given value.
This method does not require a DataTable. To avoid collision with patterns, any literal text you want to appear in the output should be surrounded by single quotes, except for the single quote, which should be doubled: e. Describes how numeric columns should be formatted. Formatting options include specifying a prefix symbol such as a dollar sign or the punctuation to use as a thousands marker. NumberFormat supports the following options, passed in to the constructor:.
A number specifying how many digits to display after the decimal. The default is 2. If you specify more digits than the number contains, it will display zeros for the smaller values. Truncated values will be rounded 5 rounded up. A format string. When provided, all other options are ignored, except negativeColor. The format string is a subset of the ICU pattern set. Enables you to merge the values of designated columns into a single column, along with arbitrary text.
This formatter does not follow the conventions for the constructor and the format method. See the Methods section below for instructions. Does not take an options object. Instead, it takes a string pattern parameter. This is a string that describes which column values to put into the destination column, along with any arbitrary text. Embed placeholders in your string to indicate a value from another column to embed. The index is an index in the srcColumnIndices array from the format method below.
Sample code The following example demonstrates a constructor for a pattern that creates an anchor element, with the first and second elements taken from the format method:. The following example demonstrates how to combine data from two columns to create an email address. It uses a DataView object to hide the original source columns:.
The following objects are available to send queries for data to an external data source, such as Google Spreadsheets. Sets the query to automatically call the send method every specified duration number of seconds , starting from the first explicit call to send.
If you use this method, you should call it before calling the send method. Cancel this method either by calling it again with zero the default , or by calling abort. Represents a response of a query execution as received from the data source. An instance of this class is passed as an argument to the callback function that was set when Query.
The API provides several functions to help you display custom error messages to your users. This container can be either the visualization container element, or a container just for errors. If you specify the visualization containe element, the error message will be displayed above the visualization.
Then call the appropriate function below to show, or remove, the error message. All functions are static functions in the namespace google. You can see an example custom error in the Query Wrapper Example. Adds an error display block to the specified page element, with specified text and formatting. String ID value that identifies the error object created, or null if the response didn't indicate an error.
This is a unique value on the page, and can be used to remove the error or find its containing element. Pass a query response and error message container to this method: if the query response indicates a query error, displays an error message in the specified page element.
If the query response is null, the method will throw a JavaScript error. Pass your QueryResponse received in your query handler to this message to display an error. Removes all error blocks from a specified container. If the specified container does not exist, this will throw an error. Retrieves a handle to the container element holding the error specified by errorID. Most visualizations fire events to indicate something has occurred. As a user of the chart, you would often want to listen to these events.
If you code your own visualization , you might also want to trigger such events on your own. The following methods enable developers to listen to events, remove existing event handlers or trigger events from inside a visualization. Call this method to register to receive events fired by a visualization hosted on your page.
You should document what event arguments, if any, will be passed to the handling function. A listener handler for the new listener. The handler can be used to later remove this listener if needed by calling google. This is identical to addListener , but is intended for events that should only be listened to once.
Subsequent throws of the event will not invoke the handling function. An example of when this is useful: every draw causes a ready event to be thrown. If you want only the first ready to execute your code, you'll want addOneTimeListener rather than addListener. Called by visualization implementers. Call this method from your visualization to fire an event with an arbitrary name and set of values.
Here is an example of a visualization that throws a method named "select" when its onclick method is called. It does not pass back any values. Every visualization should expose the following set of required and optional methods and properties. However, note that there is no type checking to enforce these standards, so you should read the documentation for each visualization.
Note: These methods are in the namespace of the visualization, not the google. Several upgrades to the Google Earth software are available. This discussion covers the standard version available for free for personal or educational use. Navigation in Google Earth will be fairly intuitive for students who have grown up in an age of clicking and dragging, mouse wheels, and video games.
Those who are not familiar with the interface may wish to take a look at one of the guides in the text box below. These guides describe the basics of browsing in Google Earth better than I can.
Nonetheles, I will summarize some of the basics here. Google Earth allows the user to view true-color images draped over topography for most of the globe, at varying resolutions mainly depending on the browser's "eye altitude" height above ground.
The user can navigate pan either by clicking and dragging part of the field of view with the mouse, by using the arrow keys, or by using a set of navigation arrows displayed in the main Google Earth viewer window. The window's viewpoint can be rotated relative to the virtual globe using a sliding or rotating control on the viewer window. The viewpoint can zoom into the globe using a slider control, the mouse wheel PC or control-clicking and dragging Mac.
The viewpoint can also "tilt" from a vertical position to a nearly horizontal poisition again using a slider control. Google Earth's main attraction, however, has been its ability to display vector datasets placemarks - points, lines, and polygonal areas , raster images overlays , and 3D virtual models on top of the virtual globe. Although some placemarks and overlays are supplied with Google Earth or are directly accessible through Google Earth in the "Google Earth Community", the majority must be downloaded from the Web.
Placemarks and overlays are discussed in more detail later. This will allow you to build and use 3D objects in Google Earth. Although 3D models are fun to play with, they are less broadly useful than other types of placemarks, so I won't go into them in detail. One clever use of 3D models in an educational context, however - an exercise on visualizing wind farms - is from Noel Jenkins' Juicy Geography site. You and your students will probably find it useful to be able to measure features in Google Earth.
Here are a few hints on how to make a couple of different measurements:. One final note about Google Earth navigation: The top panel on the left side of the Google Earth window "Search" allows the user to search for a location. In my experience, the search function is not perfect: a search for Augustine Volcano, for example, returns no results, and a search for "Mount Rainier" after a search for "Tacoma, WA" returns local businesses with the word "Rainier" in their names.
Latitude and longitude can be used instead of a place name for less ambiguous searching. As mentioned above, one of the most appealing aspects of Google Earth is the ability to import and plot information on top of the virtual globe.
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