Store data about a group of patients in a table. You can perform calculations and store results in the same table. Also, you can annotate the table to describe your work and the variables of the table.

First, create workspace variables that have the patient data. The variables can have any data types but must have the same number of rows.

LastName = {'Sanchez';'Johnson';'Li';'Diaz';'Brown'}; Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80];

Create a table,T, as a container for the workspace variables. Thetablefunction uses the workspace variable names as the names of the table variables inT．A table variable can have multiple columns. For example, theBloodPressurevariable in T is a 5-by-2 array.

T = table(LastName,Age,Smoker,Height,Weight,BloodPressure)

T=5×6 tableLastName Age Smoker Height Weight BloodPressure ___________ ___ ______ ______ ______ _____________ {'Sanchez'} 38 true 71 176 124 93 {'Johnson'} 43 false 69 163 109 77 {'Li' } 38 true 64 131 125 83 {'Diaz' } 40 false 67 133 117 75 {'Brown' } 49 true 64 119 122 80

You can use dot indexing to access table variables. For example, calculate the mean height of the patients using the values inT.Height．

meanHeight = mean(T.Height)

meanHeight = 67

Calculate body mass index (BMI), and add it as a new table variable. You also can add and name table variables in one step, using dot syntax.

T.BMI = (T.Weight*0.453592)./(T.Height*0.0254).^2

T=5×7 tableLastName Age Smoker Height Weight BloodPressure BMI ___________ ___ ______ ______ ______ _____________ ______ {'Sanchez'} 38 true 71 176 124 93 24.547 {'Johnson'} 43 false 69 163 109 77 24.071 {'Li' } 38 true 64 131 125 83 22.486 {'Diaz' } 40 false 67 133 117 75 20.831 {'Brown' } 49 true 64 119 122 80 20.426

Annotate the table with a description of the BMI calculation. You can annotateTand its variables using metadata accessed throughT.Properties．

T.Properties.Description ='Patient data, including body mass index (BMI) calculated using Height and Weight'; T.Properties

ans = TableProperties属性:描述: 'Patient data, including body mass index (BMI) calculated using Height and Weight' UserData: [] DimensionNames: {'Row' 'Variables'} VariableNames: {1x7 cell} VariableDescriptions: {} VariableUnits: {} VariableContinuity: [] RowNames: {} CustomProperties: No custom properties are set. Use addprop and rmprop to modify CustomProperties.

Access all the data from a table as a matrix, using the name of the second dimension of the table.

Create a table that has five rows of data about a set of patients.

Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80]; T = table(Age,Smoker,Height,Weight,BloodPressure)

T=5×5 tableAge Smoker Height Weight BloodPressure ___ ______ ______ ______ _____________ 38 true 71 176 124 93 43 false 69 163 109 77 38 true 64 131 125 83 40 false 67 133 117 75 49 true 64 119 122 80

Display the names of the table dimensions using theDimensionNamesproperty. The default name of the second dimension isVariables．

T.Properties.DimensionNames

ans =1x2 cell{'Row'} {'Variables'}

Access the table data as a matrix using the syntaxT.Variables．This syntax is equivalent to accessing all the contents using curly brace syntax,T{:,:}．If the table data cannot be concatenated into a matrix, then an error message is raised.

T.Variables

ans =5×638 1 71 176 124 93 43 0 69 163 109 77 38 1 64 131 125 83 40 0 67 133 117 75 49 1 64 119 122 80

Rename the second dimension. If you change the name, then you can use the new name to access the data.

T.Properties.DimensionNames{2} ='PatientData'; T.PatientData

ans =5×638 1 71 176 124 93 43 0 69 163 109 77 38 1 64 131 125 83 40 0 67 133 117 75 49 1 64 119 122 80

Preallocate a table by specifying its size and the data types of the variables. Thetablefunction fills the variables with default values that are appropriate for the data types you specify. It also gives the variables default names, but you also can assign variable names of your own. Preallocation provides room for data you add to the table later.

sz = [4 3]; varTypes = {'double','datetime','string'}; T = table('Size',sz,'VariableTypes',varTypes)

T=4×3 tableVar1 Var2 Var3 ____ ____ _________ 0 NaT  0 NaT  0 NaT  0 NaT 

To specify names for the variables, use the'VariableNames'name-value pair argument.

varNames = {'Temperature','Time','Station'}; T2 = table('Size',sz,'VariableTypes',varTypes,'VariableNames',varNames)

T2=4×3 tableTemperature Time Station ___________ ____ _________ 0 NaT  0 NaT  0 NaT  0 NaT 

Add rows of data to the first two rows ofT2．Preallocation can be a useful technique when your code adds one row of data, or a few rows of data, at a time. Instead of growing the table every time you add a row, you can fill in table variables that already have room for your data.

T2(1,:) = {75,datetime('now'),"S1"}; T2(2,:) = {68,datetime('now')+1,"S2"}

T2=4×3 tableTemperature Time Station ___________ ____________________ _________ 75 01-Sep-2021 09:50:40 "S1" 68 02-Sep-2021 09:50:40 "S2" 0 NaT  0 NaT 

You can encapsulate a row of data values in a cell array. When you assign a row from a cell array, elements from the cell array are assigned to the row in the table.

Create a table from arrays. To specify table variable names, use the'VariableNames'name-value pair argument. For example, you can use'VariableNames'to specify names when the other input arguments are not workspace variables.

T = table(categorical({'M';'F';'M'}),[45;32;34],．..{'NY';'CA';'MA'},logical([1;0;0]),．..'VariableNames',{'Gender','Age','State','Vote'})

T=3×4 tableGender Age State Vote ______ ___ ______ _____ M 45 {'NY'} true F 32 {'CA'} false M 34 {'MA'} false

Create a table with the state names as row names. You can specify both the'VariableNames'and'RowNames'name-value pairs when using thetablefunction.

T = table(categorical({'M';'F';'M'}),[45;32;34],logical([1;0;0]),．..'VariableNames',{'Gender','Age','Vote'},．..'RowNames',{'NY';'CA';'MA'})

T=3×3 tableGender Age Vote ______ ___ _____ NY M 45 true CA F 32 false MA M 34 false

Specify row names for a table. Tables do not have to have row names, but if you specify them, then you can index into a table by row name. You also can access the set of row names using the name of the first dimension of a table.

Create arrays containing patient data.

LastName = {'Sanchez';'Johnson';'Lee';'Diaz';'Brown'}; Age = [38;43;38;40;49]; Height = [71;69;64;67;64]; Weight = [176;163;131;133;119];

Create a table containing the arrays. SpecifyLastNameas the source of row names for the table. The table has only three variables. The row names are not a table variable, but instead a property of the table.

T = table(Age,Weight,Height,'RowNames',LastName)

T=5×3 tableAge Weight Height ___ ______ ______ Sanchez 38 176 71 Johnson 43 163 69 Lee 38 131 64 Diaz 40 133 67 Brown 49 119 64

Since the rows have row names, you can index into the rows ofTby name.

T('Lee',:)

ans=1×3 tableAge Weight Height ___ ______ ______ Lee 38 131 64

To specify multiple rows, use a cell array.

T({'Lee','Brown'},:)

ans=2×3 tableAge Weight Height ___ ______ ______ Lee 38 131 64 Brown 49 119 64

To access all the row names ofTas a cell array, use the syntaxT.Row．By default,Rowis the name of the first dimension of a table.

T.Row

ans =5x1 cell{'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Change the name of the first dimension. If you change the name, then you can access the row names using the new name.

T.Properties.DimensionNames{1} ='LastNames'; T.LastNames

ans =5x1 cell{'Sanchez'} {'Johnson'} {'Lee' } {'Diaz' } {'Brown' }

Starting in R2017a, you can create strings using double quotes, and add string arrays as table variables.

FlightNum = [1261;547;3489]; Customer = ["Jones";"Brown";"Smith"]; Date = datetime(2016,12,20:22)'; Rating = categorical(["Good";"Poor";"Fair"]); Comment = ["Flight left on time, not crowded";．.."Late departure, ran out of dinner options";．.."Late, but only by half an hour. Otherwise fine."]; T = table(FlightNum,Customer,Date,Rating,Comment)

T=3×5 tableFlightNum Customer Date Rating Comment _________ ________ ___________ ______ _________________________________________________ 1261 "Jones" 20-Dec-2016 Good "Flight left on time, not crowded" 547 "Brown" 21-Dec-2016 Poor "Late departure, ran out of dinner options" 3489 "Smith" 22-Dec-2016 Fair "Late, but only by half an hour. Otherwise fine."

To use the text in a string array as row names, convert the string array to a cell array of character vectors. Then create a table with row names.

Customer = cellstr(Customer); T = table(FlightNum,Date,Rating,Comment,'RowNames',Customer)

T=3×4 tableFlightNum Date Rating Comment _________ ___________ ______ _________________________________________________ Jones 1261 20-Dec-2016 Good "Flight left on time, not crowded" Brown 547 21-Dec-2016 Poor "Late departure, ran out of dinner options" Smith 3489 22-Dec-2016 Fair "Late, but only by half an hour. Otherwise fine."

Create workspace variables containing snowfall totals on different dates at three locations. These variables are row vectors.

Date = {'12/25/11','1/2/12','1/23/12','2/7/12','2/15/12'}; location1 = [20 5 13 0 17]; location2 = [18 9 21 5 12]; location3 = [26 10 16 3 15];

One way to create a table from these variables is to call thetablefunction with the syntaxT = table(Date',location1',location2',location3')．Because the workspace variables are row vectors, you must transpose them to put them into the table as column-oriented data. Therefore, the input arguments are expressions, not simple variables. As a result,tablecreatesTwith the default variable namesVar1,Var2,Var3, andVar4．You can assign more meaningful names toT.Properties.VariableNamesafter you createT．But, it might be more convenient to create an empty table, and then add variables one at a time with new names.

Create an empty table. Transpose the workspace variables and add them to the table as column vectors. As part of assigning each workspace variable intoT, provide a meaningful name for the table variable.

T = table; T.Date = Date'; T.Natick = location1'; T.Boston = location2'; T.Worcester = location3'

T=5×4 tableDate Natick Boston Worcester ____________ ______ ______ _________ {'12/25/11'} 20 18 26 {'1/2/12' } 5 9 10 {'1/23/12' } 13 21 16 {'2/7/12' } 0 5 3 {'2/15/12' } 17 12 15

Starting in R2019b, you can specify table variable names that are not valid MATLAB® identifiers. Such variable names can include spaces, non-ASCII characters, and can have any character as the leading character. When you access such a variable name, enclose it quotation marks.

创建一个表存储s data about a set of patients. Start with their ages and status as smokers.

Age = [38;43;38;40;49]; Smoker = logical([1;0;1;0;1]); Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80]; T = table(Age,Smoker)

T=5×2 tableAge Smoker ___ ______ 38 true 43 false 38 true 40 false 49 true

Add the blood pressure readings with the variable name'29-May-2019 Blood Pressure Reading'．You can use dot syntax to add or access the variable. Since its name is not a valid MATLAB identifier, use parentheses and quotation marks with dot syntax.

T.('29-May-2019 Blood Pressure Reading') = BloodPressure

T=5×3 table吸烟者年龄29日——2019年5月,血压阅读_________ __________________________________ 38 true 124 93 43 false 109 77 38 true 125 83 40 false 117 75 49 true 122 80

When table variable names are valid MATLAB identifiers, you can use dot syntax without parentheses and quotation marks.

T.Height = Height; T.Weight = Weight

T=5×5 tableAge Smoker 29-May-2019 Blood Pressure Reading Height Weight ___ ______ __________________________________ ______ ______ 38 true 124 93 71 176 43 false 109 77 69 163 38 true 125 83 64 131 40 false 117 75 67 133 49 true 122 80 64 119

索引Tusing variable names.

T (:, {'Age','Smoker','29-May-2019 Blood Pressure Reading'})

ans=5×3 table吸烟者年龄29日——2019年5月,血压阅读_________ __________________________________ 38 true 124 93 43 false 109 77 38 true 125 83 40 false 117 75 49 true 122 80