Analyzing Histograms

You can use the Histogram tool that is available in the Tools box to visualize and analyze the distribution of intensity and scalar values over a set interval and to extract basic measurements, such as the minimum, maximum, mean, and median values within the selected data.

Click the Histogram tool on the Data Properties and Settings panel to plot a distribution, as shown in the following screen capture.

Histogram Analysis dialog

Histogram Analysis dialog

You can use the Histogram tool to analyze image data, regions of interest, as well as the scalar values contained in a multi-ROI.

The following options are available for analyzing histograms of image data.

Histogram options
  Description
Tools panel The tools at the top of the dialog let you to pan, zoom, and reset the histogram, as well as save the figure and export the plotted values in the comma-separated values (*.csv extension) file format (see Histogram Tools).
Histogram Displays the plotted values, in which each column represents a range of the values and the height of a column corresponds to how many values are in that range.

Y log

If selected, the Y-axis will be plotted in log scale.
Bin count

Determines the interval in which values will be binned.

Note It is especially important to specify the optimal bin size. Bins that are too wide can hide important details about distribution while bins that are too narrow can cause spikes just by coincidence.
Measurements

Lets you select the measurements that will be computed (see Measurements). Measurements are shown on the histogram and in the Statistics box.

Note Measurements are calculated from the histogram, not directly from the data.
Dataset* / Scalar slot**

For regions of interest, lets you select the dataset from which values will be extracted.

For multi-ROIs, lets you select the scalar slot from which values will be extracted.
Show legend If selected, a legend with the selected measurements will be superimposed on the plotted values.
Statistics Shows the value of the selected measurement(s).

Copy to Clipboard

Copies the selected statistics to the clipboard, which can be pasted into any word processing or spreadsheet application.

* Available for regions of interest only.
** Available for multi-ROIs only.

The following measurements can be extracted from the selected image data.

Measurements
  Description
5th Percentile Is the value below which 5% of the values in the distribution may be found.
95th Percentile Is the value below which 95% of the values in the distribution may be found.
Full Width Half Maximum Is the width of the curve as measured between points on the Y-axis which are at the peak half maximum level.
Maximum Indicates the maximum intensity value within the distribution.
Mean Indicates the mean intensity value within the distribution.
Median Indicates the median intensity value within the distribution.
Minimum Indicates the minimum intensity value within the distribution.
Mode Is the most commonly occurring value within the distribution.
Standard Deviation Indicates the standard deviation of intensity values. Shown as the range from the mean value on the histogram.
Sum Is the integral of all intensities of all of the pixels.

The tools at the top of the Histogram dialog let you to pan, zoom, and reset the histogram, as well as save the figure and export data.

Histogram tools
 

 

 Description

Pan

Pans or zooms the figure as follows:

  • Drag left or right to pan the figure.
  • Right-click and then drag left to zoom out or drag right to zoom in on the X-axis.

Zoom

Zooms in or out on the figure, as follows:

  • Drag down to zoom in on the X axis.
  • Drag up to zoom out on the X axis.

Reset

Resets the original view of the figure.

Save

Saves the figure as an image. Figures can be saved as a bitmap image in the JPEG, PNG, and TIFF file formats, as a vector graphic in the EPS or SVG file formats, or in the PDF file format. The figure can also be saved as raw data or in PG code for LaTeX.

Settings

Settings

Opens the Figure options dialog, shown below.

Figure options dialog

You can edit the figure title, as well as choose a range, label, and scale for the X and Y axes, as follows:

  • Edit the title of the histogram in the Title edit box, if required.
  • Edit the minimum and maximum values for the X and Y axes, as required.
  • Edit the labels applied to the X and Y axes, as required.
  • Choose scaling — Linear or Log — for each axis, as required.
Export

Exports the plotted values in the comma-separated values (*.csv extension) file format.

You can use the Histogram tool that is available in the Tools box to visualize and analyze the distribution of intensity over a set interval to plot the histogram and extract basic measurements, such as the minimum, maximum, mean, and median intensity values within the selected data.

  1. Select the required image data in the Data Properties and Settings panel.
  2. Click the Histogram button in the Tools box in the bottom section of the Data Properties and Settings panel.

    The histogram of the selected image data appears.

  3. Do the following, as required.
    • Plot the Y-axis of the histogram in log scale.
    • Set the optimal bin size.
    • Select the required measurements (see Measurements).

      • Note You can add a legend to the histogram by checking Show legend.

    • Adjust the figure with the tools at the top of the dialog (see Histogram Tools).

      Note You can also save an image of the histogram or export the plotted data in the CSV file format.

You can use the Histogram tool that is available in the Tools box to visualize and analyze the distribution of intensity values of image data that corresponds to the labeled voxels of the region of interest. Values are calculated over a set interval to plot the histogram and extract basic measurements, such as the minimum, maximum, mean, and median intensity values within the corresponding image data.

  1. Select the required region of interest in the Data Properties and Settings panel.
  2. Click the Histogram button in the Tools box in the bottom section of the Data Properties and Settings panel.
  3. Select the dataset from which the intensity values will be extracted in the Dataset drop-down menu.

    The histogram of the selected image data that corresponds to the labeled voxels of the ROI appears.

    Histogram Analysis dialog

  4. Do the following, as required.
    • Plot the Y-axis of the histogram in log scale.
    • Set the optimal bin size.
    • Select the required measurements (see Measurements).

      • Note You can add a legend to the histogram by checking Show legend.

    • Adjust the figure with the tools at the top of the dialog (see Histogram Tools).

      Note You can also save an image of the histogram or export the plotted data in the CSV file format.

You can use the Histogram tool that is available in the Tools box to visualize and analyze the distribution of scalar values contained in a multi-ROI, mesh, or other object. Values are calculated over a set interval to plot the histogram and extract basic measurements, such as the minimum, maximum, mean, and median scalar values within the selected data.

  1. Select the required multi-ROI, mesh, or other object in the Data Properties and Settings panel.
  2. Click the Histogram button in the Tools box in the Scalar information box.
  3. Select the scalar slot from which values will be extracted in the Scalar slot drop-down menu.

    The histogram of the selected scalar slot appears in the Histogram Analysis dialog.

    Histogram Analysis dialog

  4. Do the following, as required.
    • Plot the Y-axis of the histogram in log scale.
    • Set the optimal bin size.
    • Select the required measurements (see Measurements).

      • Note You can add a legend to the histogram by checking Show legend.

    • Adjust the figure with the tools at the top of the dialog (see Histogram Tools).

      Note You can also save an image of the histogram or export the plotted data in the CSV file format.