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...
- Property - select the numerical attribute to
generate the histogram.
- Number of slices - select the number of intervals (slices)
if the attribute is a number.
- Press OK to generate the histogram or Cancel to
close the dialog.
- A summary function can be chosen if
the
histogram is being generated based on a linked dataset, otherwise this
option won't be visible.
- 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.