# areaDetector Plugin NDPluginStats

## March 20, 2010

## Mark Rivers

## University of Chicago

## Contents

- Overview
- Configuration
- Screen shots

## Overview

NDPluginStats computes the following.

1. Basic statistics: minimum, maximum, mean, sigma, total, and net (background subtracted).
2. Centroid and sigma values in the X and Y dimensions.
3. Profiles of the array in the X and Y dimensions. A total of 8 profiles are calculated:
   - The average profiles in the X and Y directions.
   - The average profiles in the X and Y directions, for array elements greater than the centroid threshold.
   - The profiles in the X and Y directions at the X and Y centroid position.
   - The profiles in the X and Y directions at a user-defined X and Y cursor position.
4. A histogram of the values (e.g. number of pixels versus intensity per pixel).

Each calculcation can independently enabled and disabled. Calculations 1 and 4 can be perfomed on arrays of any dimension. Calculations 2 and 3 are restricted to 2-D arrays.

NDPluginStats inherits from NDPluginDriver. The NDPluginStats class documentation describes this class in detail.

NDPluginStats.h defines the following parameters. It also implements all of the standard plugin parameters from NDPluginDriver. The EPICS database NDStats.template provide access to these parameters, listed in the following table. Note that to reduce the width of this table the parameter index variable names have been split into 2 lines, but these are just a single name, for example `NDPluginStatsComputeStatistics`.

Parameter Definitions in NDPluginStats.h and EPICS Record Definitions in NDStats.template
Parameter index variable | asyn interface | Access | Description | drvInfo string | EPICS record name | EPICS record type
--- | --- | --- | --- | --- | --- | ---
Basic statistics

NDPluginStats
ComputeStatistics

asynInt32

r/w

Flag to control whether to compute statistics for this array (0=No, 1=Yes). Not computing statistics reduces CPU load. Basic statistics computations are quite fast, since they involve mostly double precision addition, with 1 multiply to compute sigma, per array element.

COMPUTE_STATISTICS

$(P)$(R)ComputeStatistics
$(P)$(R)ComputeStatistics_RBV

bo
bi

NDPluginStats BgdWidth | asynInt32 | r/w | Width of the background in pixels to use when computing net counts. 0=no background subtraction, so the net counts is the same as the total counts. | BGD_WIDTH | $(P)$(R)BgdWidth $(P)$(R)BgdWidth_RBV | longout longin
NDPluginStats MinValue | asynFloat64 | r/o | Minimum value in any element in the array | MIN_VALUE | $(P)$(R)MinValue_RBV | ai
NDPluginStats MaxValue | asynFloat64 | r/o | Maximum value in any element in the array | MAX_VALUE | $(P)$(R)MaxValue_RBV | ai
NDPluginStats MeanValue | asynFloat64 | r/o | Mean value in the array | MEAN_VALUE | $(P)$(R)MeanValue_RBV | ai

NDPluginStats
Total

asynFloat64

r/o

Sum (total) of all elements in the array. This is available as an ai record. The total counts are also available as epicsInt32 values in an mca record via callbacks to the drvFastSweep driver. The mca record is very useful for on-the-fly data acquisition of the total counts in the detector or in an ROI.

TOTAL

$(P)$(R)Total_RBV
$(P)$(R)TotalArray

ai
mca

NDPluginStats
Net

asynFloat64

r/o

Net (background subtracted) total of all elements in the array. The background is calculated by determining the average counts per array element in a border around the array of width NDPluginStatsBgdWidth. This average background counts per element is then subtracted from all elements inside the array. If NDPluginStatsBgdWidth is ≤ 0 then no background is computed. The net counts is available as an ai record. The net counts is also available as epicsInt32 values in an mca record via callbacks to the drvFastSweep driver. The mca record is very useful for on-the-fly data acquisition of the net counts in the detector or in an ROI.

NET

$(P)$(R)Net_RBV
$(P)$(R)NetArray

ai
mca

NDPluginStats SigmaValue | asynFloat64 | r/o | Sigma (standard deviation) of all elements in the array | SIGMA_VALUE | $(P)$(R)Sigma_RBV | ai
Centroid statistics

NDPluginStats
ComputeCentroid

asynInt32

r/w

Flag to control whether to compute the centroid statistics (0=No, 1=Yes). The centroids are computed from the average row and column profiles above the centroid threshold. These calculations are also quite fast, since they just involve addition operations for each array element.

COMPUTE_CENTROID

$(P)$(R)ComputeCentroid
$(P)$(R)ComputeCentroid_RBV

bo
bi

NDPluginStats
CentroidThreshold

asynFloat64

r/w

Threshold used when computing the centroid statistics. All array elements less than this value are set to 0 for computing the centroid statistics. It is important to set this value to ignore the "background" when computing the position and size of a "beam" image, for example.

CENTROID_THRESHOLD

$(P)$(R)CentroidThreshold
$(P)$(R)CentroidThreshold_RBV

ao
ai

NDPluginStats CentroidX | asynFloat64 | r/o | X centroid of the array above the centroid threshold. | CENTROIDX_VALUE | $(P)$(R)CentroidX_RBV | ai
NDPluginStats CentroidY | asynFloat64 | r/o | Y centroid of the array above the centroid threshold. | CENTROIDY_VALUE | $(P)$(R)CentroidY_RBV | ai
NDPluginStats SigmaX | asynFloat64 | r/o | Sigma X (width) of the distribution above the centroid threshold. | SIGMAX_VALUE | $(P)$(R)SigmaX_RBV | ai
NDPluginStats SigmaY | asynFloat64 | r/o | Sigma Y (height) of the distribution above the centroid threshold. | SIGMAY_VALUE | $(P)$(R)SigmaY_RBV | ai
NDPluginStats SigmaXY | asynFloat64 | r/o | This is the normalized value of sigmaXY, i.e. sigmaXY/(sigmaX * sigmaY). This is often called the correlation coefficient, r. It is zero if the X and Y profiles are not correlated, meaning that the distribution is not tilted with respect to the X and Y axes. | SIGMAXY_VALUE | $(P)$(R)SigmaXY_RBV | ai
X and Y Profiles
NDPluginStats ComputeProfiles | asynInt32 | r/w | Flag to control whether to compute the profiles for this array (0=No, 1=Yes). | COMPUTE_PROFILES | $(P)$(R)ComputeProfiles $(P)$(R)ComputeProfiles_RBV | bo bi
NDPluginStats ProfileSizeX | asynInt32 | r/w | Number of array elements in the X profiles. | PROFILE_SIZE_X | $(P)$(R)ProfileSizeX_RBV | longin
NDPluginStats ProfileSizeY | asynInt32 | r/w | Number of array elements in the Y profiles. | PROFILE_SIZE_Y | $(P)$(R)ProfileSizeY_RBV | longin
NDPluginStats CursorX | asynInt32 | r/w | X position of a user-defined cursor for profiles. | CURSOR_X | $(P)$(R)CursorX $(P)$(R)CursorX_RBV | longout longin
NDPluginStats CursorY | asynInt32 | r/w | Y position of a user-defined cursor for profiles. | CURSOR_Y | $(P)$(R)CursorY $(P)$(R)CursorY_RBV | longout longin
NDPluginStats ProfileAverageX | asynFloat64Array | r/o | Profile of the average row in the array, i.e. the sum of all rows in the array divided by the number of rows. | PROFILE_AVERAGE_X | $(P)$(R)ProfileAverageX_RBV | waveform
NDPluginStats ProfileAverageY | asynFloat64Array | r/o | Profile of the average column in the array, i.e. the sum of all columns in the array divided by the number of columns. | PROFILE_AVERAGE_Y | $(P)$(R)ProfileAverageY_RBV | waveform
NDPluginStats ProfileThresholdX | asynFloat64Array | r/o | Same as ProfileAverageX except that all array elements less than CentroidThreshold are set to zero when computing the average. | PROFILE_THRESHOLD_X | $(P)$(R)ProfileThresholdX_RBV | waveform
NDPluginStats ProfileThresholdY | asynFloat64Array | r/o | Same as ProfileAverageY except that all array elements less than CentroidThreshold are set to zero when computing the average. | PROFILE_THRESHOLD_Y | $(P)$(R)ProfileThresholdY_RBV | waveform
NDPluginStats ProfileCentroidX | asynFloat64Array | r/o | X profile through the array in the row defined by CentroidY. | PROFILE_CENTROID_X | $(P)$(R)ProfileCentroidX_RBV | waveform
NDPluginStats ProfileCentroidY | asynFloat64Array | r/o | Y profile through the array in the column defined by CentroidX. | PROFILE_CENTROID_Y | $(P)$(R)ProfileCentroidY_RBV | waveform
NDPluginStats ProfileCursorX | asynFloat64Array | r/o | X profile through the array in the row defined by CursorY. | PROFILE_CURSOR_X | $(P)$(R)ProfileCursorX_RBV | waveform
NDPluginStats ProfileCursorY | asynFloat64Array | r/o | Y profile through the array in the row defined by CursorX. | PROFILE_CURSOR_Y | $(P)$(R)ProfileCursorY_RBV | waveform
Array histogram
NDPluginStats ComputeHistogram | asynInt32 | r/w | Flag to control whether to compute the histogram for this array (0=No, 1=Yes). Not computing the histogram reduces CPU load. | COMPUTE_HISTOGRAM | $(P)$(R)ComputeHistogram $(P)$(R)ComputeHistogram_RBV | bo bi
NDPluginStats HistSize | asynInt32 | r/w | Number of elements (bins) in the histogram | HIST_SIZE | $(P)$(R)HistSize $(P)$(R)HistSize_RBV | longout longin
NDPluginStats HistMin | asynFloat64 | r/w | Minimum value for the histogram. All values less than or equal to this will be in the first bin of the histogram. | HIST_MIN | $(P)$(R)HistMin $(P)$(R)HistMin_RBV | ao ai
NDPluginStats HistMax | asynFloat64 | r/w | Maximum value for the histogram. All values greater than or equal to this will be in the last bin of the histogram. | HIST_MAX | $(P)$(R)HistMax $(P)$(R)HistMax_RBV | ao ai
NDPluginStats HistEntropy | asynFloat64 | r/o | Entropy of the image. This is a measure of the sharpness of the histogram, and is often a useful figure of merit for determining sharpness of focus, etc. It is defined as -SUM(BIN[i]*log(BIN[i]), where the sum is over the number of bins in the histogram and BIN[i] is the number of elements in bin i. | HIST_ENTROPY | $(P)$(R)HistEntropy_RBV | ai
NDPluginStats HistArray | asynFloat64Array | r/o | Histogram array, i.e. counts in each histogram bin. | HIST_ARRAY | $(P)$(R)Histogram_RBV | waveform

If the values of CentroidThreshold, CursorX, or CursorY are changed then the centroid and profile calculations are performed again immediately on the last array collected. Thus updated centroid statistics and profiles can be displayed even when new arrays are not being acquired. These calculations are only performed when enabled by ComputeCentroid and ComputeProfiles.

## Configuration

The NDPluginStats plugin is created with the NDStatsConfigure command, either from C/C++ or from the EPICS IOC shell.

    NDStatsConfigure(const char *portName, int queueSize, int blockingCallbacks,
                   const char *NDArrayPort, int NDArrayAddr,
                   int maxBuffers, size_t maxMemory,
                   int priority, int stackSize)

For details on the meaning of the parameters to this function refer to the detailed documentation on the NDStatsConfigure function in the NDPluginStats.cpp documentation and in the documentation for the constructor for the NDPluginStats class.

## Screen shots

The following MEDM screen provides access to the parameters in NDPluginDriver.h and NDPluginStats.h through records in NDPluginBase.template and NDStats.template.

### NDStats.adl

The following MEDM screen shows the average profile of an image in the X direction.

### NDPlot.adl

The following MEDM screen shows the profile of an image in the Y direction at the location of the user-defined cursor.

### NDPlot.adl

The following MEDM screen shows the histogram of intensities of an array.

### NDPlot.adl

The following MEDM screen combines many parameters for 5 NDPluginStats plugins on a single screen.

### NDStats5.adl

The following MEDM screen shows the MCA record containing the total counts from the Stats1 plugin. This is the total counts as a function of time, and is very useful for on-the-fly data acquisition, where the NDStats plugin computes the net or total counts in the detector or an ROI.

### mca.adl

The following MEDM screen shows the MCA record containing the net counts from the Stats1 plugin.

### mca.adl