Histogram

A Histogram is a bar graph that shows how frequently data occur within certain ranges of intervals. The height of each bar gives the frequency in the respective interval.

To generate a histogram based on a layer, it is necessary to define the attribute and the number of intervals (slices).

It is accessible through:

    Layer  > Histogram...  
  1. Property  - select the numerical attribute to generate the histogram.
  2. Number of slices - select the number of intervals (slices) if the attribute is a number.
  3. Press OK to generate the histogram or Cancel to close the dialog.
  4. A summary function can be chosen if the histogram is being generated based on a linked dataset, otherwise this option won't be visible.
  5. Read all data - If the histogram will be based on a raster file, this option becomes available. It allows the user to choose weather they want to process the whole data from a band to generate the histogram;
It is also possible to interact with the histogram plotter area highlighting some data, zooming in or out. See the details on how to do that here.

 Note: If the attribute chosen is not numeric, all unique values are treated as intervals.

Note: When the histogram is based on a raster file,  setting the number of slices to 0 means any unique pixel value will generate an interval, otherwise the pixel values will be divided within the informed number of slices.

Note: If the histogram is based on a raster file and the selected band does not inform the dummy value, or inform a wrong one, than any pixel with that value will  be used while calculating the histogram's intervals and frequencies, which can generate a histogram with unexpected frequency values.