Creating a Histogram

The histogram feature is useful to visualize the distribution of data. The histogram can also be exported as an image file and saved to the local drive.

Note that it is important to manually save any time dependent information of the histogram when exporting the image file.

Summary Statistics

The histogram chart displays summary statistics when the visualization is created:

  1. Count is the total number of observations in the dataset of a variable
  2. The minimum and maximum values describe the limits of the variable in question
  3. The mean describes the variable average
  4. Standard deviation (σ) describes how dispersed the variable values are relative to the mean
  5. *Coefficient of variation (CV) is a relative measure of variability calculated by dividing the mean value by the standard deviation
  6. *Coefficient of skewness is the symmetry of the distribution around the mean value. Typically this measure is used to help determine if the observations in a dataset meet the assumptions of a normal distribution.
  7. *Coefficient of kurtosis is a measure of the "heaviness" of the tails, or the peakedness of a distribution with respect to the length and height of the tails. Distributions that are relatively flat and have short tails will have low kurtosis values, while those that are tall and pointy with long tapering tails will have high kurtosis values.

The same statistics are displayed for a subset selection in the same side bar, as shown in the example below. See Linking and Brushing for more insight.

Screenshot

Process Steps

  1. Select "Visualizations" in the main menu
  2. Select the "Histogram" item
  3. A "Create a Histogram" window will appear
  4. In the "Dataset" field, select the desired dataset from the Data panel you wish to visualize
  5. In the "Variable" field, select the variable you wish to display in the histogram
  6. In the "Workspace" field, select the desired workspace tab to display the visualization
  7. Choose to display the visualization either in a new pane or to replace an existing visualization by selecting the corresponding pane
  8. Select "OK" to display the visualization