Access and modify table metadata properties
A table, T, has properties that store metadata
such as its variable names, row names, descriptions, and variable
units. T.Properties returns a summary of all of
the table properties.
You can access a property using T.Properties.PropNameT is the name of the table and PropName is
one of the table properties. For example, to access the VariableDescriptions property
of a table named Patients, use Patients.Properties.VariableDescriptions.
You can modify a property value using T.Properties.PropName = PT is
the name of the table, PropName is one
of the table properties, and P is the desired
property value. For example, to modify the VariableUnits property
of a table named Patients, use Patients.Properties.VariableUnits
= where PP is
a cell array of character vectors containing the specified information.
In contrast, you can access and modify variables within a table
using T.VarNameT.VarName = VT is the name of the table, VarName is
the name of the variable you want to access or modify, and V is
the variable value you want.
VariableNames — Variable namesVariable names, specified as a cell array of character vectors that are nonempty and distinct. Variable names must be valid MATLAB® variable names. The number of character vectors must equal the number of variables. MATLAB removes any leading or trailing white space from the character vectors.
If valid MATLAB identifiers are not available for use
as variable names, MATLAB uses a cell array of N character
vectors of the form {'Var1' ... 'Var where N'}N is
the number of variables. You can determine valid MATLAB variable
names using the function isvarname.
The variable names are visible when viewing the table and when
using the summary function. Furthermore, you
can use the variable names within parentheses, within curly braces,
or with dot indexing to access table data.
Example
%% Create a table T = table(['M';'M';'F';'F';'F'],[38;43;38;40;49],... [71;69;64;67;64],[176;163;131;133;119])
T =
Var1 Var2 Var3 Var4
____ ____ ____ ____
M 38 71 176
M 43 69 163
F 38 64 131
F 40 67 133
F 49 64 119 %% Modify variable names T.Properties.VariableNames = {'Gender' 'Age' 'Height' 'Weight'}
T =
Gender Age Height Weight
______ ___ ______ ______
M 38 71 176
M 43 69 163
F 38 64 131
F 40 67 133
F 49 64 119 %% Create a subtable % % Use variable names within parentheses to create a subtable. % Include al the rows, but only the variables Age and Gender. T(:,{'Age','Gender'})
ans =
Age Gender
___ ______
38 M
43 M
38 F
40 F
49 F %% Extract data from the table % % Use variable names within curly braces to extract the % numeric data from the variables Height and Weight. T{:,{'Height','Weight'}}
ans =
71 176
69 163
64 131
67 133
64 119% Use variable names with dot indexing to extract % all the data from the variable Gender. T.Gender
ans = M M F F F
RowNames — Row names{} (default) | cell array of character vectorsRow names, specified as a cell array of character vectors that are nonempty and distinct. This property can be empty, but if not empty, the number of character vectors must equal the number of rows in the table. MATLAB removes any leading or trailing white space from the character vectors. The default property value is an empty cell array.
The row names are visible when you view the table. Furthermore, you can use the row names within parentheses or curly braces to access the table data.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight,Smoker,Systolic,Diastolic); % Add row names T.Properties.RowNames = LastName; % Remove row names T.Properties.RowNames = {};
DimensionNames — Dimension names{'Row' ‘Variable'} (default) | two-element cell array of character vectorsDimension names, specified as a two-element cell array of character vectors.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight,Smoker,Systolic,Diastolic,... 'RowNames',LastName); % Add dimension names T.Properties.DimensionNames = {'Patient' 'Data'};
Description — Table description'' (default) | character vectorTable description, specified as a character vector. This description
is visible when using the summary function.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight); % Add a table description T.Properties.Description = 'Simulated patient data'; % View the summary format compact summary(T)
Description: Simulated patient data
Variables:
Gender: 100x1 char
Age: 100x1 double
Values:
min 25
median 39
max 50
Height: 100x1 double
Values:
min 60
median 67
max 72
Weight: 100x1 double
Values:
min 111
median 142.5
max 202 VariableDescriptions — Variable descriptions{} (default) | cell array of character vectorsVariable descriptions, specified as a cell array of character vectors. This property can be an empty cell array, which is the default. If the cell array is not empty, the number of character vectors must equal the number of variables. You can specify an individual empty character vector within the cell array for a variable that does not have a description.
The variable descriptions are visible when using the summary function.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight,Smoker,Systolic,Diastolic); % Add variable descriptions T.Properties.VariableDescriptions = {'' '' '' '' ... 'Has the patient ever been a smoker' ... 'Systolic Pressure' 'Diastolic Pressure'}; % View the summary format compact summary(T)
Variables:
Gender: 100x1 char
Age: 100x1 double
Values:
min 25
median 39
max 50
Height: 100x1 double
Values:
min 60
median 67
max 72
Weight: 100x1 double
Values:
min 111
median 142.5
max 202
Smoker: 100x1 logical
Description: Has the patient ever been a smoker
Values:
true 34
false 66
Systolic: 100x1 double
Description: Systolic Pressure
Values:
min 109
median 122
max 138
Diastolic: 100x1 double
Description: Diastolic Pressure
Values:
min 68
median 81.5
max 99 % Remove all the variable descriptions
T.Properties.VariableDescriptions = {};VariableUnits — Variable units{} (default) | cell array of character vectorsVariable units, specified as a cell array of character vectors. This property can be an empty cell array, which is the default. If the cell array is not empty, the number of character vectors must equal the number of variables. You can specify an individual empty character vector within the cell array for a variable that does not have units.
The variable units are visible when using the summary function.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight,Smoker,Systolic,Diastolic); % Add variable units T.Properties.VariableUnits = {'' 'Yrs' 'In' 'Lbs' '' 'mm Hg' 'mm Hg'}; % View the summary format compact summary(T)
Variables:
Gender: 100x1 char
Age: 100x1 double
Units: Yrs
Values:
min 25
median 39
max 50
Height: 100x1 double
Units: In
Values:
min 60
median 67
max 72
Weight: 100x1 double
Units: Lbs
Values:
min 111
median 142.5
max 202
Smoker: 100x1 logical
Values:
true 34
false 66
Systolic: 100x1 double
Units: mm Hg
Values:
min 109
median 122
max 138
Diastolic: 100x1 double
Units: mm Hg
Values:
min 68
median 81.5
max 99 % Remove all the variable units
T.Properties.VariableUnits = {};UserData — Additional table information{} (default) | variable containing information in any data typeAdditional table information, specified as a variable containing information in any data type.
Example
% Create a table load patients T = table(Gender,Age,Height,Weight,Smoker,Systolic,Diastolic); % Add an anonymous function to the table metadata formula = @(x) x.^2; T.Properties.UserData = formula;