ismember

Class: dataset

(Not Recommended) Dataset array elements that are members of set

The dataset data type is not recommended. To work with heterogeneous data, use the MATLAB^® table data type instead. See MATLAB table documentation for more information.

Syntax

LiA = ismember(A,B)
LiA = ismember(A,B,vars)
[LiA,LocB] = ismember(___)


Description

LiA = ismember(A,B) for dataset arrays A and B returns a vector of logical values the same length as A. The output vector, LiA, has value 1 (true) in the elements that correspond to observations in A that are also present in B, and 0 (false) otherwise.

LiA = ismember(A,B,vars) returns a vector of logical values the same length as A. The output vector, LiA, has value 1 (true) in the elements that correspond to observations in A that are also present in B for the variables specified in vars only, and 0 (false) otherwise.

[LiA,LocB] = ismember(___) also returns a vector the same length as A containing the index to the first observation in B that corresponds to each observation in A, or 0 if there is no such observation. You can use any of the previous input arguments.

Input Arguments

A	Query dataset array, containing the observations to be found in B.
B	Set dataset array. When an observation in A is found in B, for all variables or only those variables specified in vars, the corresponding element of LiA is 1.
vars	String array or cell array of character vectors containing variable names, or a vector of integers containing variable column numbers. vars indicates which variables to match observations on in A and B.

Output Arguments

LiA	Vector of logical values the same length as A. LiA has value 1 (true) when the corresponding observation in A is present in B. Otherwise, LiA has value 0 (false). If you specify vars, LiA has value 1 when the corresponding observation in A is present in B for the variables in vars only.
LocB	Vector the same length as A containing the index to the first observation in B that corresponds to each observation in A, for all variables or only those variables specified in vars.

Examples

Find Observations That Are Members of a Dataset Array

Load sample data.

load('hospital')
B = hospital(1:50,1:5);

This set dataset array, B, has 50 observations on 5 variables.

Specify a query dataset array.

rng('default')
rIx = randsample(100,10);
A = hospital(rIx,1:5)

A = 
               LastName             Sex       Age    Weight    Smoker
    YLN-495    {'COLEMAN'  }        Male      39     188       false 
    LQW-768    {'TAYLOR'   }        Female    31     132       false 
    DGC-290    {'BUTLER'   }        Male      38     184       true  
    DAU-529    {'REED'     }        Male      50     186       true  
    REV-997    {'ALEXANDER'}        Male      25     171       true  
    QEQ-082    {'COX'      }        Female    28     111       false 
    AGR-528    {'SIMMONS'  }        Male      45     181       false 
    PUE-347    {'YOUNG'    }        Female    25     114       false 
    HVR-372    {'RUSSELL'  }        Male      44     188       true  
    XUE-826    {'JACKSON'  }        Male      25     174       false 

Check which observations in A are present in B.

LiA = ismember(A,B)

LiA = 10x1 logical array

   0
   1
   0
   0
   0
   0
   0
   1
   0
   1

Display the observations in A that are present in B.

A(LiA,:)

ans = 
               LastName           Sex       Age    Weight    Smoker
    LQW-768    {'TAYLOR' }        Female    31     132       false 
    PUE-347    {'YOUNG'  }        Female    25     114       false 
    XUE-826    {'JACKSON'}        Male      25     174       false 

Find the location of the observations in B.

[~,LocB] = ismember(A,B)

LocB = 10×1

     0
    10
     0
     0
     0
     0
     0
    28
     0
    13

Display the observations in B that match observations in A.

B(LocB(LocB>0),:)

ans = 
               LastName           Sex       Age    Weight    Smoker
    LQW-768    {'TAYLOR' }        Female    31     132       false 
    PUE-347    {'YOUNG'  }        Female    25     114       false 
    XUE-826    {'JACKSON'}        Male      25     174       false