ismissing

Find missing values

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Syntax

TF = ismissing(A)
TF = ismissing(A,indicator)

Description

example

TF = ismissing(A) returns a logical array that indicates which elements of an array or table contain missing values. The size of TF is the same as the size of A.

Standard missing values depend on the data type:

  • NaN for double, single, duration, and calendarDuration

  • NaT for datetime

  • <missing> for string

  • <undefined> for categorical

  • ' ' for char

  • {''} for cell of character vectors

example

TF = ismissing(A,indicator) treats the values in indicator as missing value indicators, ignoring all default indicators listed in the previous syntax. indicator can be a single indicator or multiple indicators. For example, if A is an array of type double, then ismissing(A,[0,-99]) treats 0 and -99 as missing double values instead of NaN.

Examples

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Open Live Script

Create a row vector A that contains NaN values, and identify their location in A.

A = [3 NaN 5 6 7 NaN NaN 9];
TF = ismissing(A)
TF = 1x8 logical array

   0   1   0   0   0   1   1   0
Open Live Script

Create a table with variables of different data types and find the elements with missing values. 

dblVar = [NaN;3;5;7;9;11;13];
singleVar = single([1;NaN;5;7;9;11;13]);
cellstrVar = {'one';'three';'';'seven';'nine';'eleven';'thirteen'};
charVar = ['A';'C';'E';' ';'I';'J';'L'];
categoryVar = categorical({'red';'yellow';'blue';'violet';'';'ultraviolet';'orange'});
dateVar = [datetime(2015,1:2:10,15) NaT datetime(2015,11,15)]';
stringVar = ["a";"b";"c";"d";"e";"f";missing];

A = table(dblVar,singleVar,cellstrVar,charVar,categoryVar,dateVar,stringVar)
A=7×7 table
    dblVar    singleVar     cellstrVar     charVar    categoryVar      dateVar      stringVar
    ______    _________    ____________    _______    ___________    ___________    _________

     NaN           1       {'one'     }       A       red            15-Jan-2015    "a"      
       3         NaN       {'three'   }       C       yellow         15-Mar-2015    "b"      
       5           5       {0x0 char  }       E       blue           15-May-2015    "c"      
       7           7       {'seven'   }               violet         15-Jul-2015    "d"      
       9           9       {'nine'    }       I       <undefined>    15-Sep-2015    "e"      
      11          11       {'eleven'  }       J       ultraviolet            NaT    "f"      
      13          13       {'thirteen'}       L       orange         15-Nov-2015    <missing>

ismissing returns 1 where the corresponding element in A has a missing value. 

TF = ismissing(A)
TF = 7x7 logical array

   1   0   0   0   0   0   0
   0   1   0   0   0   0   0
   0   0   1   0   0   0   0
   0   0   0   1   0   0   0
   0   0   0   0   1   0   0
   0   0   0   0   0   1   0
   0   0   0   0   0   0   1

The size of TF is the same as the size of A.

Open Live Script

Create a table where 'NA', '', -99, NaN, and Inf represent missing values. Then, find the elements with missing values. 

dblVar = [NaN;3;Inf;7;9];
int8Var = int8([1;3;5;7;-99]);
cellstrVar = {'one';'three';'';'NA';'nine'};
charVar = ['A';'C';'E';' ';'I'];

A = table(dblVar,int8Var,cellstrVar,charVar)
A=5×4 table
    dblVar    int8Var    cellstrVar    charVar
    ______    _______    __________    _______

     NaN          1      {'one'   }       A   
       3          3      {'three' }       C   
     Inf          5      {0x0 char}       E   
       7          7      {'NA'    }           
       9        -99      {'nine'  }       I

ismissing returns 1 where the corresponding element in A has a missing value. 

id = {'NA' '' -99 NaN Inf};
TF = ismissing(A,id)
TF = 5x4 logical array

   1   0   0   0
   0   0   0   0
   1   0   1   0
   0   0   1   1
   0   1   0   0

ismissing ignores trailing white space in character arrays. Therefore, since the empty character vector, '', is specified as a missing value indicator, ismissing identifies the empty character vector in A.cellstrVar and also the blank space in A.charVar as missing values.

Input Arguments

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Input data, specified as a vector, matrix, multidimensional array, table, or timetable.

If A is a timetable, then ismissing operates on the table data only and ignores NaT or NaN values in the vector of row times.

When the input argument is a cell array, it must be a cell array of character vectors. If the input is a table or timetable with a variable of type cell, then ismissing only detects missing elements when the variable is a cell array of character vectors.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | cell | table | timetable | categorical | datetime | duration | calendarDuration

Missing value indicators, specified as a scalar, vector, or cell array. If A is an array, then indicator must be a vector. If A is a table or timetable, then indicator can also be a cell array with entries of multiple data types.

The entries of indicator indicate the values that ismissing treats as missing. Specifying indicator overrides all default standard missing indicators. If you want to add indicators while maintaining the list of standard indicators, then you must include all default indicators as elements of indicator. For example, if A is a table with categorical and numeric values, use ismissing(A,{-99,'<undefined>'}) to indicate -99 as a missing numeric value, but preserve <undefined> as a missing categorical value.

You can also use the missing value as an indicator for any missing data represented as NaN, NaT, missing, or <undefined>. If your input is a table, then missing is also an indicator for missing character vectors (' ') and missing cell arrays of character vectors ({''}).

Indicator data types match data types in the entries of A. The following are additional data type matches between the indicator and elements of A:

  • double indicators match double, single, integer, and logical entries of A.

  • string and char indicators, and indicators that are cell arrays of character vectors, match string entries of A.

  • string and char indicators match categorical entries of A.

Example: TF = ismissing(A,0) recognizes only 0 as a missing value.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | cell | datetime | duration

Tips

  • Since integer variables cannot store NaN, use a special integer value (otherwise unused) to indicate missing integer data, such as -99.

  • For more information on finding missing strings, see Test for Empty Strings and Missing Values.

Algorithms

ismissing handles leading and trailing white space differently for indicators that are cell arrays of character vectors, character arrays, or categorical arrays.

  • For cell arrays of character vectors, ismissing does not ignore indicator white space. All character vectors must match exactly.

  • For character arrays in table variables, ismissing ignores trailing white space in the indicator.

  • For categorical arrays, ismissing ignores leading and trailing white space in the indicator.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

See Also

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Topics

Introduced in R2013b

MATLAB Documentation
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