# histcounts

Compute histogram bin counts for specified variables in baseline and target data for drift detection

## Description

example

H = histcounts(DDiagnostics) returns the histogram bin counts in the table H for all variables specified for drift detection in the call to the detectdrift function.

example

H = histcounts(DDiagnostics,Variables=variables) returns the bin counts for the variables specified by variables.

## Examples

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Generate baseline and target data with two variables, where the distribution parameters of the second variable change for target data.

rng('default') % For reproducibility
baseline = [normrnd(0,1,100,1),wblrnd(1.1,1,100,1)];
target = [normrnd(0,1,100,1),wblrnd(1.2,2,100,1)];

Perform permutation testing for any drift between the baseline and target data.

DDiagnostics = detectdrift(baseline,target);

Compute the histogram bin counts for all variables.

H = histcounts(DDiagnostics)
H=2×3 table
Bins                                                         Counts_Baseline                                 Counts_Target
__________________________________________________________________________________    ____________________________________________    __________________________________________

x1    {[-3.5000 -3 -2.5000 -2 -1.5000 -1 -0.5000 0 0.5000 1 1.5000 2 2.5000 3 3.5000 4]}    {[0 1 1 3 14.0000 11 17 17 15 11 5 1 2 1 1]}    {[1 0 2 6 7.0000 13 22 24 11 8 4 2 0 0 0]}
x2    {[                       0 0.5000 1 1.5000 2 2.5000 3 3.5000 4 4.5000 5 5.5000 6]}    {[        33 23 14.0000 11 8 6 3 0 0 1 0 1]}    {[      13 32 29.0000 20 6 0 0 0 0 0 0 0]}

H is a table with three columns. histcounts divides the data into bins and computes the histogram bin counts for a variable in the baseline and target data over the common bins. The first and second rows contain the bins and counts for variables x1 and x2, respectively.

Access the histogram bin counts in the baseline data for the first variable.

H.Counts_Baseline{1}
ans = 1×15

0    1.0000    1.0000    3.0000   14.0000   11.0000   17.0000   17.0000   15.0000   11.0000    5.0000    1.0000    2.0000    1.0000    1.0000

Plot the probability density function (pdf) estimate (percent of the data in each bin) of the baseline data for variable 1.

histogram(BinEdges=H.Bins{1},BinCounts=H.Counts_Baseline{1},Normalization='probability')

You can also plot the histogram of the baseline and target data for variable 1 using the plotHistogram function.

plotHistogram(DDiagnostics,Variable=1)

For details on the data set, enter Description at the command line.

Assign the first 1000 observations as baseline data and the next 1000 as target data.

baseline = feat(1:1000,:);
target = feat(1001:2000,:);

Test for drift on all variables.

DDiagnostics = detectdrift(baseline,target);

Compute the histogram bin counts for only the first five variables.

H = histcounts(DDiagnostics,Variables=(1:5))
H=5×3 table
Bins                                                                                                      Counts_Baseline                                                                           Counts_Target
_________________________________________________________________________________________________________________________________________________    ______________________________________________________________________    ____________________________________________________________________________________________________

x1    {[                                                             -0.2000 -0.1000 0 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.8000 0.9000]}    {[                                 0 0 0 0 0 0 0 0 0 85.9000 14.1000]}    {[                                 12.4000 76.6000 2.1000 0 0 0 0.1000 0.1000 0.1000 0.1000 8.5000]}
x2    {[                                            -0.3000 -0.2000 -0.1000 0 0.1000 0.2000 0.3000 0.4000 0.5000 0.6000 0.7000 0.8000 0.9000 1 1.1000]}    {[                      0 0 0 0 0 9.9000 24 0.3000 65.8000 0 0 0 0 0]}    {[                           0.1000 0 0.1000 0.1000 0.1000 8.2000 0.3000 0 0 0 0 0 53.8000 37.3000]}
x3    {[         -0.6000 -0.5500 -0.5000 -0.4500 -0.4000 -0.3500 -0.3000 -0.2500 -0.2000 -0.1500 -0.1000 -0.0500 0 0.0500 0.1000 0.1500 0.2000 0.2500]}    {[0 19.9000 13.6000 0.3000 0.3000 0.2000 65.7000 0 0 0 0 0 0 0 0 0 0]}    {[0.1000 0.4000 8.4000 0 0 0 0 0 12.9000 4.1000 0.3000 0.2000 0.4000 8.5000 49.1000 2.7000 12.9000]}
x4    {[0 0.0100 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 0.1100 0.1200 0.1300 0.1400 0.1500 0.1600 0.1700 0.1800 0.1900 0.2000]}    {[     0 0 0 0 0 0 0 0 0 0 65.6000 33.9000 0.4000 0.1000 0 0 0 0 0 0]}    {[     34.5000 55.7000 0.9000 0 0 0 0 0 0 0 0 7.4000 0.5000 0.2000 0.3000 0 0.1000 0.3000 0 0.1000]}
x5    {[                                     0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 0.0900 0.1000 0.1100 0.1200 0.1300 0.1400 0.1500 0.1600 0.1700]}    {[                 0.3000 33.1000 0 0 0.3000 66 0.3000 0 0 0 0 0 0 0]}    {[                       0 7.5000 0.5000 0.1000 0 0 0 0.1000 0.1000 0 0.2000 91.1000 0.2000 0.2000]}

Access the histogram bin counts for the second variable in the target data.

H.Counts_Target{2}
ans = 1×14

0.1000         0    0.1000    0.1000    0.1000    8.2000    0.3000         0         0         0         0         0   53.8000   37.3000

## Input Arguments

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Diagnostics of the permutation testing for drift detection, specified as a DriftDiagnostics object returned by detectdrift.

List of variables for which to compute the histogram bin counts, specified as a string array, cell array of character vectors, or list of integer indices.

Example: Variables=["x1","x3"]

Example: Variables=(1,3)

Data Types: single | double | char | string

## Output Arguments

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Histogram bin counts, returned as a table with the following columns.

Column NameDescription
Bins

Common domain over which to evaluate the histogram bin counts for a variable.

• For categorical variables, Bins contains the categories.

• For continuous variables, Bins contains the bin edges.

Counts_BaselineHistogram bin counts for the corresponding variables in the baseline data
Counts_TargetHistogram bin counts for the corresponding variables in the target data

For each variable in H, the columns contain the bins and counts in cell arrays. To access the counts, you can index into the table; for example, to obtain the histogram bin counts for the second variable in the baseline data, use H.Counts_Baseline{2,1}.

## Algorithms

• For categorical data, detectdrift adds a 0.5 correction factor to the histogram bin counts for each bin to handle empty bins (categories). This is equivalent to the assumption that the parameter p, probability that value of the variable would be in that category, has the prior distribution Beta(0.5,0.5), (Jeffreys prior assumption for the distribution parameter).

• histcounts treats a variable as ordinal for visualization purposes in these cases:

• The variable is ordinal in either the baseline data or the target data, and the categories from both the baseline data and the target data are the same.

• The variable is ordinal in either the baseline data or the target data, and the categories of the other data set are a subset of the ordinal data.

• The variable is ordinal in both the baseline data and the target data, and categories from either data set are a subset of the other.

• If a variable is ordinal, histcounts preserves the order of the bin names.

## Version History

Introduced in R2022a