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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 ofTFis the same as the size ofA.

Standard missing values depend on the data type:

  • NaNfordouble,single,duration, andcalendarDuration

  • NaTfordatetime

  • forstring

  • forcategorical

  • ' 'forchar

  • {''}forcellof character vectors

example

TF = ismissing(A,indicator)treats the values inindicatoras missing value indicators, ignoring all default indicators listed in the previous syntax.indicatorcan be a single indicator or multiple indicators. For example, ifAis an array of typedouble, thenismissing(A,[0,-99])treats 0 and -99 as missingdoublevalues instead ofNaN.

Examples

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Open Live Script

Create a row vectorAthat containsNaNvalues, and identify their location inA.

A = [3 NaN 5 6 7 NaN NaN 9]; TF = ismissing(A)
TF =1x8 logical array0 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 tabledblVar 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  15-Sep-2015 "e" 11 11 {'eleven' } J ultraviolet NaT "f" 13 13 {'thirteen'} L orange 15-Nov-2015

ismissingreturns 1 where the corresponding element inAhas a missing value.

TF = ismissing(A)
TF =7x7 logical array1 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

的大小TFis the same as the size ofA.

Open Live Script

Create a table where'NA','',-99,NaN, andInfrepresent 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 tabledblVar int8Var cellstrVar charVar ______ _______ __________ _______ NaN 1 {'one' } A 3 3 {'three' } C Inf 5 {0x0 char} E 7 7 {'NA' } 9 -99 {'nine' } I

ismissingreturns 1 where the corresponding element inAhas a missing value.

id = {'NA'''-99 NaN Inf}; TF = ismissing(A,id)
TF =5 x4逻辑阵列1 0 0 0 0 0 0 0 1 0 1 0 0 0 1 1 0 1 0 0

ismissingignores trailing white space in character arrays. Therefore, since the empty character vector,'', is specified as a missing value indicator,ismissingidentifies the empty character vector inA.cellstrVarand also the blank space inA.charVaras missing values.

Input Arguments

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

IfAis a timetable, thenismissingoperates on the table data only and ignoresNaTorNaNvalues 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 typecell, thenismissingonly 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. IfAis an array, thenindicatormust be a vector. IfAis a table or timetable, thenindicatorcan also be a cell array with entries of multiple data types.

The entries ofindicatorindicate the values thatismissingtreats as missing. Specifyingindicatoroverrides 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 ofindicator. For example, ifAis a table withcategoricaland numeric values, useismissing(A,{-99,''})to indicate-99as a missing numeric value, but preserveas a missingcategoricalvalue.

You can also use themissingvalue as an indicator for any missing data represented asNaN,NaT,missing, or. If your input is a table, thenmissingis also an indicator for missing character vectors (' ') and missing cell arrays of character vectors ({''}).

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

  • doubleindicators matchdouble,single, integer, andlogicalentries ofA.

  • stringandcharindicators, and indicators that are cell arrays of character vectors, matchstringentries ofA.

  • stringandcharindicators matchcategoricalentries ofA.

Example:TF = ismissing(A,0)recognizes only0as 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 storeNaN, use a special integer value (otherwise unused) to indicate missing integer data, such as-99.

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

Algorithms

ismissinghandles 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,ismissingdoes not ignore indicator white space. All character vectors must match exactly.

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

  • For categorical arrays,ismissingignores 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

万博1manbetx

Introducing Deep Learning with MATLAB

Introducing Deep Learning with MATLAB

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