dataset class -

Arrays for statistical data

Description

Dataset arrays are used to collect heterogeneous data and metadata including variable and observation names into a single container variable. Dataset arrays are suitable for storing column-oriented or tabular data that are often stored as columns in a text file or in a spreadsheet, and can accommodate variables of different types, sizes, units, etc.

Dataset arrays can contain different kinds of variables, including numeric, logical, character, categorical, and cell. However, a dataset array is a different class than the variables that it contains. For example, even a dataset array that contains only variables that are double arrays cannot be operated on as if it were itself a double array. However, using dot subscripting, you can operate on variable in a dataset array as if it were a workspace variable.

You can subscript dataset arrays using parentheses much like ordinary numeric arrays, but in addition to numeric and logical indices, you can use variable and observation names as indices.

Construction

Use the dataset constructor to create a dataset array from variables in the MATLAB workspace. You can also create a dataset array by reading data from a text or spreadsheet file. You can access each variable in a dataset array much like fields in a structure, using dot subscripting. See the following section for a list of operations available for dataset arrays.

dataset

Construct dataset array

Methods

cat	Concatenate dataset arrays
cellstr	Create cell array of strings from dataset array
dataset2cell	Convert dataset array to cell array
datasetfun	Apply function to dataset array variables
disp	Display dataset array
display	Display dataset array
double	Convert dataset variables to double array
end	Last index in indexing expression for dataset array
export	Write dataset array to file
get	Access dataset array properties
grpstats	Summary statistics by group for dataset arrays
horzcat	Horizontal concatenation for dataset arrays
isempty	True for empty dataset array
join	Merge observations
length	Length of dataset array
ndims	Number of dimensions of dataset array
numel	Number of elements in dataset array
replacedata	Replace dataset variables
set	Set and display properties
single	Convert dataset variables to single array
size	Size of dataset array
sortrows	Sort rows of dataset array
stack	Stack data from multiple variables into single variable
subsasgn	Subscripted assignment to dataset array
subsref	Subscripted reference for dataset array
summary	Print summary of dataset array
unique	Unique observations in dataset array
unstack	Unstack data from single variable into multiple variables
vertcat	Vertical concatenation for dataset arrays

Properties

A dataset array D has properties that store metadata (information about your data). Access or assign to a property using P = D.Properties.PropName or D.Properties.PropName = P, where PropName is one of the following:

Description	String describing data set
DimNames	Two-element cell array of strings giving names of dimensions of data set
ObsNames	Cell array of nonempty, distinct strings giving names of observations in data set
Units	Units of variables in data set
UserData	Variable containing additional information associated with data set
VarDescription	Cell array of strings giving descriptions of variables in data set
VarNames	Cell array giving names of variables in data set

Copy Semantics

Value. To learn how this affects your use of the class, see Comparing Handle and Value Classes in the MATLAB Object-Oriented Programming documentation.

Examples

Load a dataset array from a .mat file and create some simple subsets:

load hospital
h1 = hospital(1:10,:)
h2 = hospital(:,{'LastName' 'Age' 'Sex' 'Smoker'})

% Access and modify metadata
hospital.Properties.Description
hospital.Properties.VarNames{4} = 'Wgt'

% Create a new dataset variable from an existing one
hospital.AtRisk = hospital.Smoker | (hospital.Age > 40)

% Use individual variables to explore the data
boxplot(hospital.Age,hospital.Sex)
h3 = hospital(hospital.Age<30,...
   {'LastName' 'Age' 'Sex' 'Smoker'})

% Sort the observations based on two variables
h4 = sortrows(hospital,{'Sex','Age'})

See Also

genvarname | tdfread | textscan | xlsread

How To

• Dataset Arrays for Heterogeneous Data

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