groupcounts

Number of group elements

Syntax

G = groupcounts(T,groupvars)

G = groupcounts(T,groupvars,groupbins)

G = groupcounts(___,Name,Value)

B = groupcounts(A)

B = groupcounts(A,groupbins)

B = groupcounts(___,Name,Value)

[B,BG,BP] = groupcounts(A,___)

Description

Table Data

G = groupcounts(T,groupvars) returns the unique grouping variable combinations for table or timetable T, the number of members in each group, and the percentage of the data each group represents in the range [0, 100]. Groups are defined by rows in the variables in groupvars that have the same unique combination of values. Each row of the output table corresponds to one group. For example, G = groupcounts(T,"HealthStatus") returns a table with the count and percentage of each group in the variable HealthStatus.

G = groupcounts(T,groupvars,groupbins) specifies to bin rows in groupvars according to binning scheme groupbins prior to grouping. For example, G = groupcounts(T,"SaleDate","year") returns the group counts and group percentages for all sales in T within each year according to the grouping variable SaleDate.

G = groupcounts(___,Name,Value) specifies additional grouping properties using one or more name-value arguments for any of the previous syntaxes. For example, G = groupcounts(T,"Category1","IncludeMissingGroups",false) excludes the group made from missing data of type categorical indicated by <undefined> in Category1.

Array Data

B = groupcounts(A) returns the number of members in each group in vector, matrix, or cell array A. Groups are defined by rows in the column vectors in A that have the same unique combination of values. Each row of B contains the count for one group.

B = groupcounts(A,groupbins) specifies to bin the data according to binning scheme groupbins prior to grouping.

B = groupcounts(___,Name,Value) specifies additional grouping properties using one or more name-value arguments for either of the previous syntaxes for an input array.

[B,BG,BP] = groupcounts(A,___) returns additional group information. BG is the unique grouping vector combinations corresponding to the rows in B. BP is the percentage of the data each group count in B represents. The percentages are in the range [0, 100].

Examples

Group Table Variables

Compute the number of elements in each group based on table data.

Create a table T that contains information about eight individuals.

HealthStatus = categorical(["Poor"; "Good"; "Fair"; "Fair"; "Poor"; "Excellent"; "Good"; "Excellent"]);
Smoker = logical([1; 0; 0; 1; 1; 0; 0; 1]);
Weight = [176; 153; 131; 133; 119; 120; 140; 129];
T = table(HealthStatus,Smoker,Weight)

T=8×3 table
    HealthStatus    Smoker    Weight
    ____________    ______    ______

     Poor           true       176  
     Good           false      153  
     Fair           false      131  
     Fair           true       133  
     Poor           true       119  
     Excellent      false      120  
     Good           false      140  
     Excellent      true       129  

Group the individuals by health status, and return the number of and percentage of individuals in each group.

G1 = groupcounts(T,"HealthStatus")

G1=4×3 table
    HealthStatus    GroupCount    Percent
    ____________    __________    _______

     Excellent          2           25   
     Fair               2           25   
     Good               2           25   
     Poor               2           25   

Group the individuals by health status and smoker status, and return the number of and percentage of individuals in each group. By default, groupcounts suppresses groups with zero elements, so some unique combinations of the grouping variable values are not returned.

G2 = groupcounts(T,["HealthStatus","Smoker"])

G2=6×4 table
    HealthStatus    Smoker    GroupCount    Percent
    ____________    ______    __________    _______

     Excellent      false         1          12.5  
     Excellent      true          1          12.5  
     Fair           false         1          12.5  
     Fair           true          1          12.5  
     Good           false         2            25  
     Poor           true          2            25  

To return a row for each group, including those with zero elements, specify IncludeEmptyGroups as true.

G3 = groupcounts(T,["HealthStatus","Smoker"],"IncludeEmptyGroups",true)

G3=8×4 table
    HealthStatus    Smoker    GroupCount    Percent
    ____________    ______    __________    _______

     Excellent      false         1          12.5  
     Excellent      true          1          12.5  
     Fair           false         1          12.5  
     Fair           true          1          12.5  
     Good           false         2            25  
     Good           true          0             0  
     Poor           false         0             0  
     Poor           true          2            25  

Specify Group Bins

Group data according to specified bins.

Create a timetable containing sales information for days within a single month.

TimeStamps = datetime([2017 3 4; 2017 3 2; 2017 3 15; 2017 3 10; ...
                       2017 3 14; 2017 3 31; 2017 3 25; ...
                       2017 3 29; 2017 3 21; 2017 3 18]);
Profit = [2032 3071 1185 2587 1998 2899 3112 909 2619 3085]';
ItemsSold = [14 13 8 5 10 16 8 6 7 11]';
TT = timetable(TimeStamps,Profit,ItemsSold)

TT=10×2 timetable
    TimeStamps     Profit    ItemsSold
    ___________    ______    _________

    04-Mar-2017     2032        14    
    02-Mar-2017     3071        13    
    15-Mar-2017     1185         8    
    10-Mar-2017     2587         5    
    14-Mar-2017     1998        10    
    31-Mar-2017     2899        16    
    25-Mar-2017     3112         8    
    29-Mar-2017      909         6    
    21-Mar-2017     2619         7    
    18-Mar-2017     3085        11    

Compute the group counts by the total items sold, binning the groups into intervals of item numbers.

G = groupcounts(TT,"ItemsSold",[0 4 8 12 16])

G=3×3 table
    disc_ItemsSold    GroupCount    Percent
    ______________    __________    _______

       [4, 8)             3           30   
       [8, 12)            4           40   
       [12, 16]           3           30   

Compute the group counts binned by day of the week.

G = groupcounts(TT,"TimeStamps","dayname")

G=5×3 table
    dayname_TimeStamps    GroupCount    Percent
    __________________    __________    _______

        Tuesday               2           20   
        Wednesday             2           20   
        Thursday              1           10   
        Friday                2           20   
        Saturday              3           30   

Find Duplicate Array Elements

Determine which elements in a vector appear more than once.

Create a column vector with values between 1 and 5.

A = [1 1 2 2 3 5 3 3 1 4]';

Determine the unique groups in the vector and count the group members.

[B,BG] = groupcounts(A)

B = 5×1

     3
     2
     3
     1
     1

BG = 5×1

     1
     2
     3
     4
     5

Determine which elements in the vector appear more than once by creating a logical index for the groups with a count larger than 1. Index into the groups to return the vector elements that are duplicated.

duplicates = BG(B > 1)

duplicates = 3×1

     1
     2
     3

Multiple Grouping Vectors for Vector Input

Compute the group counts for a set of people grouped by their health status and smoker status.

Store information about eight individuals as three vectors of different types.

HealthStatus = categorical(["Poor"; "Good"; "Fair"; "Fair"; "Poor"; "Excellent"; "Good"; "Excellent"]);
Smoker = logical([1; 0; 0; 1; 1; 0; 0; 1]);
Weight = [176; 153; 131; 133; 119; 120; 140; 129];

Grouping by health status and smoker status, compute the group counts. Specify three outputs to also return the groups BG and group count percentages BP.

BG is a cell array containing two vectors that describe the groups as you look at their elements row-wise. For instance, the first row of BG{1} indicates that the individuals in the first group have a health status Excellent, and the first row of BG{2} indicates that they are nonsmokers. Finally, BP contains the percentage of members in each group for the corresponding groups in BG.

[B,BG,BP] = groupcounts({HealthStatus,Smoker},"IncludeEmptyGroups",true);
B

B = 8×1

     1
     1
     1
     1
     2
     0
     0
     2

BG{1}

ans = 8x1 categorical
     Excellent 
     Excellent 
     Fair 
     Fair 
     Good 
     Good 
     Poor 
     Poor 

BG{2}

ans = 8x1 logical array

   0
   1
   0
   1
   0
   1
   0
   1

BP

BP = 8×1

   12.5000
   12.5000
   12.5000
   12.5000
   25.0000
         0
         0
   25.0000

Input Arguments

T — Input table

table | timetable

Input table, specified as a table or timetable.

A — Input array

column vector | matrix | cell array

Input array, specified as a column vector, group of column vectors stored as a matrix, or cell array of column vectors, character row vectors, or matrices.

groupvars — Grouping variables or vectors

scalar | vector | matrix | cell array | function handle | table vartype subscript

Grouping variables or vectors, specified as one of the options in this table. For table or timetable input data, groupvars indicates which variables to use to compute groups in the data. Other variables not specified by groupvars are not operated on and do not pass through to the output.

Option	Description	Examples
Variable name	A character vector or string scalar specifying a single table variable name	'Var1' "Var1"
Vector of variable names	A cell array of character vectors or string array, where each element is a table variable name	{'Var1' 'Var2'} ["Var1" "Var2"]
Scalar or vector of variable indices	A scalar or vector of table variable indices	1 [1 3 5]
Logical vector	A logical vector whose elements each correspond to a table variable, where true includes the corresponding variable and false excludes it	[true false true]
Function handle	A function handle that takes a table variable as input and returns a logical scalar	@isnumeric
vartype subscript	A table subscript generated by the vartype function	vartype("numeric")

Example: groupcounts(T,"Var3")

groupbins — Binning scheme

"none" (default) | scalar | vector | cell array

Binning scheme, specified as one of these options:

• "none", indicating no binning

• A list of bin edges, specified as a numeric vector, or a datetime vector for datetime grouping variables or vectors

• A number of bins, specified as a positive integer scalar

• A time duration, specified as a scalar of type duration or calendarDuration indicating bin widths (for datetime or duration grouping variables or vectors only)

• A cell array listing binning methods for each grouping variable or vector

• A time bin for datetime and duration grouping variables or vectors only, specified as one of these strings.

  Value	Description	Data Type
  "second"	Each bin is 1 second.	datetime and duration
  "minute"	Each bin is 1 minute.	datetime and duration
  "hour"	Each bin is 1 hour.	datetime and duration
  "day"	Each bin is 1 calendar day. This value accounts for daylight saving time shifts.	datetime and duration
  "week"	Each bin is 1 calendar week.	datetime only
  "month"	Each bin is 1 calendar month.	datetime only
  "quarter"	Each bin is 1 calendar quarter.	datetime only
  "year"	Each bin is 1 calendar year. This value accounts for leap days.	datetime and duration
  "decade"	Each bin is 1 decade (10 calendar years).	datetime only
  "century"	Each bin is 1 century (100 calendar years).	datetime only
  "secondofminute"	Bins are seconds from 0 to 59.	datetime only
  "minuteofhour"	Bins are minutes from 0 to 59.	datetime only
  "hourofday"	Bins are hours from 0 to 23.	datetime only
  "dayofweek"	Bins are days from 1 to 7. The first day of the week is Sunday.	datetime only
  "dayname"	Bins are full day names such as "Sunday".	datetime only
  "dayofmonth"	Bins are days from 1 to 31.	datetime only
  "dayofyear"	Bins are days from 1 to 366.	datetime only
  "weekofmonth"	Bins are weeks from 1 to 6.	datetime only
  "weekofyear"	Bins are weeks from 1 to 54.	datetime only
  "monthname"	Bins are full month names such as "January".	datetime only
  "monthofyear"	Bins are months from 1 to 12.	datetime only
  "quarterofyear"	Bins are quarters from 1 to 4.	datetime only

When multiple grouping variables or vectors are specified, you can provide a single binning method that is applied to all grouping variables or vectors, or a cell array containing a binning method for each grouping variable or vector such as {"none",[0 2 4 Inf]}.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: G = groupcounts(T,groupvars,groupbins,IncludedEdge="right")

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: G = groupcounts(T,groupvars,groupbins,"IncludedEdge","right")

IncludedEdge — Included bin edge

"left" (default) | "right"

Included bin edge, specified as either "left" or "right", indicating which end of the bin interval is inclusive.

This name-value argument can be specified only when groupbins is specified, and the value applies to all binning schemes for all grouping variables or vectors.

IncludeMissingGroups — Missing groups indicator

true or 1 (default) | false or 0

Missing groups indicator, specified as a numeric or logical 1 (true) or 0 (false). When the value of IncludeMissingGroups is true, groupcounts displays groups made up of missing values, such as NaN. When the value of IncludeMissingGroups is false, groupcounts does not display the missing value groups.

IncludeEmptyGroups — Empty groups indicator

false or 0 (default) | true or 1

Empty groups indicator, specified as a numeric or logical 0 (false) or 1 (true). When the value of IncludeEmptyGroups is false, groupcounts does not display groups with zero elements. When the value of IncludeEmptyGroups is true, groupcounts displays the empty groups.

Output Arguments

G — Output table

table

Output table for table or timetable input data, returned as a table. G contains the computed groups, number of elements in each group, and percentages represented by each group count. For a single grouping variable, the output groups are sorted according to the order returned by the unique function with the "sorted" option.

B — Group counts

column vector

Group counts for array input data, returned as a column vector. B contains the number of elements in each group.

BG — Groups

column vector | cell array of column vectors

Groups for array input data, returned as a column vector or cell array of column vectors. For a single grouping vector, the output groups are sorted according to the order returned by the unique function with the "sorted" option.

For more than one input vector, BG is a cell array containing column vectors of equal length. Information for each group is contained in the elements of a row across all vectors in BG. Each group maps to the corresponding row of the output array B.

BP — Group count percentages

column vector

Group count percentages for array input data, returned as a column vector. BP contains a percentage in the range [0, 100] for each group in B.

Tips

• When making many calls to groupcounts, consider converting grouping variables to type categorical or logical when possible for improved performance. For example, if you have a string array grouping variable (such as HealthStatus with elements "Poor", "Fair", "Good", and "Excellent"), you can convert it to a categorical variable using the command categorical(HealthStatus).

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

Usage notes and limitations:

• The first input argument does not support cell arrays.

• The groupvars argument does not support function handles.

• The IncludeEmptyGroups name-value argument is not supported.

• The order of the groups might be different compared to in-memory groupcounts calculations.

• When grouping by discretized datetime arrays, the categorical group names are different compared to in-memory groupcounts calculations.

For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• All input arguments except for the input data must be constant.

• Sparse inputs are not supported.

• Binning scheme is not supported for datetime or duration data.

• If the number of group variables can change at runtime, the second output BG is a cell array.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History

Introduced in R2019a

R2022a: Code generation support

Generate C or C++ code for the groupcounts function. For usage notes and limitations, see C/C++ Code Generation.

R2021a: Percentages automatically included in table outputs

When groupcounts operates on data in a table or timetable, the output contains an additional table variable for the percentages. The percentages are in the range [0, 100] and are included in the table variable Percent.

Any code that references specific table variables is unaffected. However, you might need to update code that depends on the number of variables in the output table.