# Documentation

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## Add and Delete Table Variables

This example shows how to add and delete column-oriented variables in a table. You also can edit tables using the Variables Editor.

Load the sample patients data and create two tables. Create one table, `T`, with information collected from a patient questionnaire and create another table, `T1`, with data measured from the patient.

```load patients T = table(Age,Gender,Smoker); T1 = table(Height,Weight,Systolic,Diastolic);```

Display the first five rows of each table.

`T(1:5,:)`
```ans=5x3 table Age Gender Smoker ___ ________ ______ 38 'Male' true 43 'Male' false 38 'Female' false 40 'Female' false 49 'Female' false ```
`T1(1:5,:)`
```ans=5x4 table Height Weight Systolic Diastolic ______ ______ ________ _________ 71 176 124 93 69 163 109 77 64 131 125 83 67 133 117 75 64 119 122 80 ```

The table `T` has 100 rows and 3 variables.

The table `T1` has 100 rows and 4 variables.

### Add Variables by Concatenating Tables

Add variables to the table, `T`, by horizontally concatenating it with `T1`.

`T = [T T1];`

Display the first five rows of the table, `T`.

`T(1:5,:)`
```ans=5x7 table Age Gender Smoker Height Weight Systolic Diastolic ___ ________ ______ ______ ______ ________ _________ 38 'Male' true 71 176 124 93 43 'Male' false 69 163 109 77 38 'Female' false 64 131 125 83 40 'Female' false 67 133 117 75 49 'Female' false 64 119 122 80 ```

The table, `T`, now has 7 variables and 100 rows.

If the tables that you are horizontally concatenating have row names, `horzcat` concatenates the tables by matching the row names. Therefore, the tables must use the same row names, but the row order does not matter.

### Add and Delete Variables by Name

First create a new variable for blood pressure as a horizontal concatenation of the two variables `Systolic` and `Diastolic`. Then, delete the variables `Systolic` and `Diastolic` by name using dot indexing.

```T.BloodPressure = [T.Systolic T.Diastolic]; T.Systolic = []; T.Diastolic = [];```

Alternatively, you can also use parentheses with named indexing to delete the variables `Systolic` and `Diastolic` at once, `T(:,{'Systolic','Diastolic'}) = [];`.

Display the first five rows of the table, `T`.

`T(1:5,:)`
```ans=5x6 table Age Gender Smoker Height Weight BloodPressure ___ ________ ______ ______ ______ _____________ 38 'Male' true 71 176 124 93 43 'Male' false 69 163 109 77 38 'Female' false 64 131 125 83 40 'Female' false 67 133 117 75 49 'Female' false 64 119 122 80 ```

`T` now has 6 variables and 100 rows.

Add a new variable, `BMI`, in the table, `T`, to contain the body mass index for each patient. `BMI` is a function of height and weight.

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

The operators `./` and `.^` in the calculation of `BMI` indicate element-wise division and exponentiation, respectively.

Display the first five rows of the table, `T`.

`T(1:5,:)`
```ans=5x7 table Age Gender Smoker Height Weight BloodPressure BMI ___ ________ ______ ______ ______ _____________ ______ 38 'Male' true 71 176 124 93 24.547 43 'Male' false 69 163 109 77 24.071 38 'Female' false 64 131 125 83 22.486 40 'Female' false 67 133 117 75 20.831 49 'Female' false 64 119 122 80 20.426 ```

`T` has 100 rows and 7 variables.

### Delete Variables by Number

Delete the third variable, `Smoker`, and the sixth variable, `BloodPressure`, from the table.

`T(:,[3,6]) = [];`

Display the first five rows of the table, `T`.

`T(1:5,:)`
```ans=5x5 table Age Gender Height Weight BMI ___ ________ ______ ______ ______ 38 'Male' 71 176 24.547 43 'Male' 69 163 24.071 38 'Female' 64 131 22.486 40 'Female' 67 133 20.831 49 'Female' 64 119 20.426 ```

`T` has 100 rows and 5 variables.