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 = datastore('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'         
    :       :
    :       :

Test whether the underlying data type of the first table variable Year is single.

tf = isaUnderlying(tt.Year,'single')

tf =

   tall logical 

   0

Determine the actual underlying data type of Year.

udt = classUnderlying(tt.Year)

udt =

  1×6 tall char array

double