Histogram

A histogram is a graphical representations showing a visual impression of the distribution of data. It is an estimate of the probability distribution of a continuous variable. A histogram consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval. The height of a rectangle is also equal to the frequency density of the interval, i.e. , the frequency divided bu the width of the interval. The total area of  the histogram is equal to the number of values.

The categories (intervals) must be adjacent, and are often chosen to be of the same size. The rectangles of a histogram are drawn so that they touch each other to indicate that the original variable is continuous.

In TerraView, a histogram is created based on a layer's data, therefore, it is accessible through:

        Layer  > Histogram...

Once a layer has been selected and the menu item has been clicked the following screen will be opened:
Histogram creation dialog




 Interface description:
 
        1 - Property selection -  This component lists all available properties that may be used to generate a histogram.
        2 - Number of slices - Used to define the number of intervals of the histogram that will be generated.
        3 - Help button - Opens the help window.
        4 - Ok button - Creates the histogram based on the information provided.
        5 - Cancel button - Closes the dialog without generating a new histogram.

Note: In some cases, the user is not allowed to select a number of slices. This happens when the type of the chosen property does not support the calculation required to split the data among the intervals, for example when the data is a text. If this happens, all unique values are treated as intervals. In this case, the dialog will be as follows:


Histogram creation dialog - using a text based property.


Once the histogram chart is generated  it will show up on TerraView as the following screen:

Histogram Chart.



 Interface description:

1 - Graphic style button -  Opens up the chart style dialog.
2 -Title - Displays the title of the histogram chart.
3 - Y Axis label - Displays the Y axis' title.
4 - X Axis label - Displays the X axis' title.
5 - Plot area - The are where the chart will be drawn.

By clicking on the Graphic Style button it is possible to configure some of the charts elements.  Once clicked, the following screen will be shown:


Histogram style.



Interface Description:

1 - Histogram style item -  When selected, displays the window used to configure a histogram's style.
2 - Histogram Style tab - Displays the window used to configure a histogram's style.
3 - Fill button - Displays the window used to configure the histogram's bar fill.
4 - Stroke button - Displays the window used to configure the histogram's bar stroke.
5 - Help button - Opens the help window.
6 - Apply button - Closes the window applying the changes that were made.
7 - Cancel button - Closes the window without applying any changes.

For a detailed description of the general style options, check the chart style documentation.