Statistics Measurements


The Statistics Measurement tool is used to compute the value of a statistical estimator for pixels within a rectangular image region. The estimator is selected from the Statistics Properties dialog and may range from a basic quantity like the Mean to a more complex computation such as SigmaClip or Skewness.

This command uses the Image Cursor to permit profile plots within the same region without having to re-position.

Measuring a Single Image or Image Set

If an Image Set is open in the Image Window, you can choose whether to measure only the currently displayed member of the image set or compute the statistic for the entire image set. This is done using the Measure Image Set button in the Image Set Flags group on the Image Bar. When the button face shows a "1", then only the current (one) image is measured, otherwise, the entire image set is measured.

Measurement Results

Results of statistics measurements are tabulated in either a Statistics Measurements window used by all image windows or a private measurement pane owned by the Image window. These hold the measurements in a Grid Control that includes menu commands for activities like sorting, rearranging, copying, saving, graphing, and opening in Microsoft Excel. Below, the first example below shows a Statistics Measurements window containing the Median value for members of an Image Set. The second example shows a measurement pane in which the Statistics Properties were changed to compare different estimators and parameters over the same rectangle in a single image.

The measurement table columns are described in the table below.

Statistics Quantities

#

The sequence number of the measurement.

Image

The name of the image that was measured

Estimator

The name of the estimator used for the measurement. If the measurement has parameters (e.g., "SigmaClip"), then the parameters are listed in the Notes column.

Value

The estimator value.

Std Dev

The standard deviation of values inside the region. Note: Some measurements do not calculate the Standard Deviation (example: Minimum) and will insert the value "0" as a placeholder in the table.

Minimum

The minimum value inside the region.

Maximum

The maximum value inside the region

Region

Description of the pixel region that was measured. This description uses the following format:

[MinCol:MaxCol, MinRow:MaxRow]

Pixels

The pixel count inside the region.

Notes

Initially, this contains information about the estimator parameters. The cells containing Notes may be edited to change this information or add details about the particular measurement.

Tip for Usage

When making many measurements or repeatedly changing the properties, it may be advantageous to detach the Measurements Toolbar and move it onto the image, as shown below:

Related Topics

Measuring Images, Statistics Properties, Report Windows, Measurement Panes, Image Set, Image Cursor