All tall tables and arrays belong to thetallclass. However, theunderlying数据type of a tall array can vary.

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

varnames = {“年”,'UniqueCarrier'}; ds = datastore('airlinesmall.csv','TreatAsMissing','NA',...'SelectedVariableNames',varnames); tt = tall(ds)

tt = Mx2 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 tablettand the first table variableYear.

class(tt)

ans = 'tall'

class(tt.Year)

ans = 'tall'

Determine the underlying data types oftt, as well as theYearandUniqueCarriertable variables.

classUnderlying(tt)

ans = 1x5 tall char array 'table'

classUnderlying(tt.Year)

ans = 1x6 tall char array 'double'

classUnderlying(tt.UniqueCarrier)

ans = 1x4 tall char array 'cell'

In some cases, the result returned byclassUnderlyingis an unevaluated tall array. Unevaluated tall arrays can be evaluated using thegatherfunction to bring the result into memory.