classUnderlying

Class of underlying data in tall array

Syntax

C = classUnderlying(X)

Description

C = classUnderlying(X) returns the class of the data stored inside tall array X.

Examples

Determine Underlying Class of Tall Arrays

All tall tables and arrays belong to the tall class. However, the underlying data type of a tall array can vary.

Create a datastore for the airlinesmall.csv data set. Select a subset of the variables to work with, and treat 'NA' values as missing data so that datastore replaces them with NaN values. Convert the datastore into a tall table.

varnames = {'Year', 'UniqueCarrier'};
ds = tabularTextDatastore('airlinesmall.csv','TreatAsMissing','NA',...
    'SelectedVariableNames',varnames);
tt = tall(ds)

tt =

  M×2 tall table

    Year    UniqueCarrier
    ____    _____________

    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
    1987       {'PS'}    
     :            :
     :            :

Determine the class of the tall table tt and the first table variable Year.

class(tt)

ans = 
'tall'

class(tt.Year)

ans = 
'tall'

Determine the underlying data types of tt, as well as the Year and UniqueCarrier table variables.

classUnderlying(tt)

ans =

  1×5 tall char array

    'table'

classUnderlying(tt.Year)

ans =

  1×6 tall char array

    'double'

classUnderlying(tt.UniqueCarrier)

ans =

  1×4 tall char array

    'cell'

In some cases, the result returned by classUnderlying is an unevaluated tall array. Unevaluated tall arrays can be evaluated using the gather function to bring the result into memory.

Input Arguments

X — Input array

tall array

Input array, specified as a tall array.

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

Output Arguments

C — Underlying class

tall array

Underlying class, returned as a tall array.

Tips

• Use isaUnderlying to test whether a tall array has a particular underlying data type.

Extended Capabilities

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

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The classUnderlying function supports GPU array input with these usage notes and limitations:

• See classUnderlying (Parallel Computing Toolbox).

Version History

Introduced in R2016b