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Combine two tables or timetables by rows using key variables

`C = join(A,B)`

`C = join(A,B,Name,Value)`

```
[C,ib]
= join(___)
```

merges tables or timetables `C`

= join(`A,B`

)`A`

and `B`

by
matching up rows, using all the variables with the same names as key variables. The key values must be
common to both `A`

and `B`

but can appear in
different orders. `A`

and `B`

can be tables,
timetables, or one of each.

If

`A`

is a table, then`join`

returns`C`

as a table.If

`A`

is a timetable, then`join`

returns`C`

as a timetable.

`join`

retains all the variables from `A`

and
appends the corresponding contents from the nonkey variables of
`B`

.

The row labels of `A`

and `B`

can be key
variables. Row labels are the row names of a table, or the row times of a
timetable.

joins the tables or timetables with additional options specified by one or more
`C`

= join(`A,B`

,`Name,Value`

)`Name,Value`

pair arguments.

For example, you can specify which variables to use as key variables.

Create a table, `A`

.

A = table({'Janice','Jonas','Javier','Jerry','Julie'}',[1;2;1;2;1],... 'VariableNames',{'Employee' 'Department'})

`A=`*5×2 table*
Employee Department
________ __________
'Janice' 1
'Jonas' 2
'Javier' 1
'Jerry' 2
'Julie' 1

Create a table, `B`

, with a variable in common with `A`

.

B = table([1 2]',{'Mary' 'Mona'}',... 'VariableNames',{'Department' 'Manager'})

`B=`*2×2 table*
Department Manager
__________ _______
1 'Mary'
2 'Mona'

Create a new table, `C`

, containing data from tables `A`

and `B`

. Use the `join`

function to repeat and append `Manager`

data from table `B`

to the data from table `A`

, based on the key variable, `Department`

.

C = join(A,B)

`C=`*5×3 table*
Employee Department Manager
________ __________ _______
'Janice' 1 'Mary'
'Jonas' 2 'Mona'
'Javier' 1 'Mary'
'Jerry' 2 'Mona'
'Julie' 1 'Mary'

Create a table, `A`

.

A = table([5;12;23;2;6],... {'cereal';'pizza';'salmon';'cookies';'pizza'},... 'VariableNames',{'Age','FavoriteFood'},... 'RowNames',{'Amy','Bobby','Holly','Harry','Sally'})

`A=`*5×2 table*
Age FavoriteFood
___ ____________
Amy 5 'cereal'
Bobby 12 'pizza'
Holly 23 'salmon'
Harry 2 'cookies'
Sally 6 'pizza'

Create a table, `B`

, with one variable in common with `A`

.

B = table({'cereal';'cookies';'pizza';'salmon';'cake'},... [110;160;140;367;243],... {'B';'D';'B-';'A';'C-'},... 'VariableNames',{'FavoriteFood','Calories','NutritionGrade'})

`B=`*5×3 table*
FavoriteFood Calories NutritionGrade
____________ ________ ______________
'cereal' 110 'B'
'cookies' 160 'D'
'pizza' 140 'B-'
'salmon' 367 'A'
'cake' 243 'C-'

Create a new table, `C`

, with data from tables `A`

and `B`

. The variable in common, `FavoriteFood`

, is used as a key variable by the `join`

function.

C = join(A,B)

`C=`*5×4 table*
Age FavoriteFood Calories NutritionGrade
___ ____________ ________ ______________
Amy 5 'cereal' 110 'B'
Bobby 12 'pizza' 140 'B-'
Holly 23 'salmon' 367 'A'
Harry 2 'cookies' 160 'D'
Sally 6 'pizza' 140 'B-'

Table `C`

does not include information from the last row of table `B`

about `'cake'`

because there is no corresponding entry in table `A`

.

Create a table, `A`

.

A = table([10;4;2;3;7],[5;4;9;6;1],[10;3;8;8;4])

`A=`*5×3 table*
Var1 Var2 Var3
____ ____ ____
10 5 10
4 4 3
2 9 8
3 6 8
7 1 4

Create a table, `B`

, giving `Var2`

of table `B`

the same contents as `Var2`

from table `A`

.

B = table([6;1;1;6;8],[5;4;9;6;1])

`B=`*5×2 table*
Var1 Var2
____ ____
6 5
1 4
1 9
6 6
8 1

Create a new table, `C`

, containing data from tables `A`

and `B`

. Use `Var2`

in tables `A`

and `B`

as the key variable to the `join`

function.

C = join(A,B,'Keys','Var2')

`C=`*5×4 table*
Var1_A Var2 Var3 Var1_B
______ ____ ____ ______
10 5 10 6
4 4 3 1
2 9 8 1
3 6 8 6
7 1 4 8

`join`

adds a unique suffix to the nonkey variable, `Var1`

, to distinguish the data from tables `A`

and `B`

.

Create a new table with data from tables `A`

and `B`

. If any nonkey variables have the same name in both tables, keep only the copy from table `A`

.

Create a table, `A`

.

A = table([10;4;2;3;7],[5;4;9;6;1])

`A=`*5×2 table*
Var1 Var2
____ ____
10 5
4 4
2 9
3 6
7 1

Create a table, `B`

, giving `Var2`

of table `B`

the same contents as `Var2`

from table `A`

.

B = table([6;1;1;6;8],[5;4;9;6;1],[10;3;8;8;4])

`B=`*5×3 table*
Var1 Var2 Var3
____ ____ ____
6 5 10
1 4 3
1 9 8
6 6 8
8 1 4

Create a new table, `C`

, with data from tables `A`

and `B`

. Use `Var2`

as a key variable to the `join`

function and keep only the copy of `Var1`

from table `A`

. The output table `C`

does not contain the `Var1`

data from table `B`

.

C = join(A,B,'Keys','Var2','KeepOneCopy','Var1')

`C=`*5×3 table*
Var1 Var2 Var3
____ ____ ____
10 5 10
4 4 3
2 9 8
3 6 8
7 1 4

Create a table, `A`

.

A = table(['M';'M';'F';'F';'F'],[38;43;38;40;49],... 'VariableNames',{'Gender' 'Age'},... 'RowNames',{'Smith' 'Johnson' 'Williams' 'Jones' 'Brown'})

`A=`*5×2 table*
Gender Age
______ ___
Smith M 38
Johnson M 43
Williams F 38
Jones F 40
Brown F 49

Create a table, `B`

, such that the rows of `A`

and the rows of `B`

have a one-to-one correspondence.

B = table([64;69;67;71;64],... [119;163;133;176;131],... [122 80; 109 77; 117 75; 124 93; 125 83],... 'VariableNames',{'Height' 'Weight' 'BloodPressure'},... 'RowNames',{'Brown' 'Johnson' 'Jones' 'Smith' 'Williams'})

`B=`*5×3 table*
Height Weight BloodPressure
______ ______ _____________
Brown 64 119 122 80
Johnson 69 163 109 77
Jones 67 133 117 75
Smith 71 176 124 93
Williams 64 131 125 83

Create a new table, `C`

, with data from tables `A`

and `B`

. Use the row names as keys to the `join`

function.

C = join(A,B,'Keys','RowNames')

`C=`*5×5 table*
Gender Age Height Weight BloodPressure
______ ___ ______ ______ _____________
Smith M 38 71 176 124 93
Johnson M 43 69 163 109 77
Williams F 38 64 131 125 83
Jones F 40 67 133 117 75
Brown F 49 64 119 122 80

The rows of `C`

are in the same order as `A`

.

Create a table, `A`

.

A = table([10;4;2;3;7],[5;4;9;6;1],[10;3;8;8;4])

`A=`*5×3 table*
Var1 Var2 Var3
____ ____ ____
10 5 10
4 4 3
2 9 8
3 6 8
7 1 4

Create a table, `B`

, giving `Var2`

of table `B`

the same contents as `Var1`

from table `A`

, but in a different order.

B = table([6;1;1;6;8],[2;3;4;7;10])

`B=`*5×2 table*
Var1 Var2
____ ____
6 2
1 3
1 4
6 7
8 10

Create a new table, `C`

, containing data from tables `A`

and `B`

. Use `Var1`

from table `A`

with `Var2`

from table `B`

as key variables to the `join`

function.

[C,ib] = join(A,B,'LeftKeys',1,'RightKeys',2)

`C=`*5×4 table*
Var1_A Var2 Var3 Var1_B
______ ____ ____ ______
10 5 10 8
4 4 3 1
2 9 8 6
3 6 8 1
7 1 4 6

`ib = `*5×1*
5
3
1
2
4

`C`

is the horizontal concatenation of `A`

and `B(ib,2)`

.

Create two timetables that have the same row times but different variables.

Traffic = [0.8 0.9 0.1 0.7 0.9]'; Noise = [0 1 1.5 2 2.3]'; A = timetable(hours(1:5)',Traffic,Noise)

`A=`*5×2 timetable*
Time Traffic Noise
____ _______ _____
1 hr 0.8 0
2 hr 0.9 1
3 hr 0.1 1.5
4 hr 0.7 2
5 hr 0.9 2.3

Distance = [0.88 0.86 0.91 0.9 0.86]'; B = timetable(hours(1:5)',Distance)

`B=`*5×1 timetable*
Time Distance
____ ________
1 hr 0.88
2 hr 0.86
3 hr 0.91
4 hr 0.9
5 hr 0.86

Merge the timetables. `join`

uses the row times as the key variables.

C = join(A,B)

`C=`*5×3 timetable*
Time Traffic Noise Distance
____ _______ _____ ________
1 hr 0.8 0 0.88
2 hr 0.9 1 0.86
3 hr 0.1 1.5 0.91
4 hr 0.7 2 0.9
5 hr 0.9 2.3 0.86

Create a timetable and a table.

Measurements = [0.13 0.22 0.31 0.42 0.53 0.57 0.67 0.81 0.90 1.00]'; Device = ['A';'B';'A';'B';'A';'B';'A';'B';'A';'B']; A = timetable(seconds(1:10)',Measurements,Device)

`A=`*10×2 timetable*
Time Measurements Device
______ ____________ ______
1 sec 0.13 A
2 sec 0.22 B
3 sec 0.31 A
4 sec 0.42 B
5 sec 0.53 A
6 sec 0.57 B
7 sec 0.67 A
8 sec 0.81 B
9 sec 0.9 A
10 sec 1 B

Device = ['A';'B']; Accuracy = [0.023;0.037]; B = table(Device,Accuracy)

`B=`*2×2 table*
Device Accuracy
______ ________
A 0.023
B 0.037

Merge the timetable and table. `Device`

is the key variable because both `A`

and `B`

have a variable with that name. `C`

is a timetable.

C = join(A,B)

`C=`*10×3 timetable*
Time Measurements Device Accuracy
______ ____________ ______ ________
1 sec 0.13 A 0.023
2 sec 0.22 B 0.037
3 sec 0.31 A 0.023
4 sec 0.42 B 0.037
5 sec 0.53 A 0.023
6 sec 0.57 B 0.037
7 sec 0.67 A 0.023
8 sec 0.81 B 0.037
9 sec 0.9 A 0.023
10 sec 1 B 0.037

`A,B`

— Input tablestables | timetables

Input tables, specified as tables, timetables, or as one of each. For all
key variables, each row of `A`

must match exactly one row
in `B`

.

Specify optional
comma-separated pairs of `Name,Value`

arguments. `Name`

is
the argument name and `Value`

is the corresponding value.
`Name`

must appear inside quotes. You can specify several name and value
pair arguments in any order as `Name1,Value1,...,NameN,ValueN`

.

`'Keys',2`

uses the second variable in
`A`

and the second variable in `B`

as key
variables.`'Keys'`

— Variables to use as keyspositive integer | vector of positive integers | character vector | cell array of character vectors | string array | logical vector |

`'RowNames'`

Variables to use as keys, specified as the comma-separated pair
consisting of `'Keys'`

and a positive integer, vector
of positive integers, character vector, cell array of character vectors,
string array, logical vector, or `'RowNames'`

.

You cannot use the `'Keys'`

name-value pair argument
with the `'LeftKeys'`

and
`'RightKeys'`

name-value pair arguments.

Row labels can be key variables. Row labels are the row names of a
table or the row times of a timetable. You can specify
`'Keys'`

as the row labels only, as one or more
variables in `A`

and `B`

, or as row
labels and variables together.

If you specify the value `'RowNames'`

, then
`join`

uses the row names of `A`

and row names of `B`

as keys. In this case, there must
be a row in `B`

for every row in `A`

.
You cannot specify `'RowNames'`

when
`A`

is a timetable.

**Example: **`'Keys',[1 3]`

uses the first and third
variables from `A`

and `B`

as key
variables.

`'LeftKeys'`

— Variables to use as keys in `A`

positive integer | vector of positive integers | character vector | cell array of character vectors | string array | logical vector

Variables to use as keys in `A`

, specified as the
comma-separated pair consisting of `'LeftKeys'`

and a
positive integer, vector of positive integers, character vector, cell
array of character vectors, string array, or logical vector.

You must use the `'LeftKeys'`

name-value pair
argument in conjunction with the `'RightKeys'`

name-value pair argument. `'LeftKeys'`

and
`'RightKeys'`

both must specify the same number of
key variables. `join`

pairs key values in
`A`

and `B`

based on their
order.

Row labels can be key variables. Row labels are the row names of a
table or the row times of a timetable. You can specify
`'LeftKeys'`

as the row labels of
`A`

, as one or more variables in
`A`

, or as row labels and variables
together.

**Example: **`'LeftKeys',1`

uses only the first variable
in `A`

as a key variable.

`'RightKeys'`

— Variables to use as keys in `B`

positive integer | vector of positive integers | character vector | cell array of character vectors | string array | logical vector

Variables to use as keys in `B`

, specified as the
comma-separated pair consisting of `'RightKeys'`

and a
positive integer, vector of positive integers, character vector, cell
array of character vectors, string array, or logical vector.

You must use the `'RightKeys'`

name-value pair
argument in conjunction with the `'LeftKeys'`

name-value pair argument. `'LeftKeys'`

and
`'RightKeys'`

both must specify the same number of
key variables. `join`

pairs key values in
`A`

and `B`

based on their
order.

Row labels can be key variables. Row labels are the row names of a
table or the row times of a timetable. You can specify
`'RightKeys'`

as the row labels of
`B`

, as one or more variables in
`B`

, or as row labels and variables
together.

**Example: **`'RightKeys',3`

uses only the third variable
in `B`

as a key variable.

`'LeftVariables'`

— Variables from `A`

to include in `C`

positive integer | vector of positive integers | character vector | cell array of character vectors | string array | logical vector

Variables from `A`

to include in
`C`

, specified as the comma-separated pair consisting
of `'LeftVariables'`

and a positive integer, vector of
positive integers, character vector, cell array of character vectors,
string array, or logical vector.

You can use `'LeftVariables'`

to include or exclude
key variables, as well as nonkey variables, from `C`

.
However, you cannot include row names or row times from
`A`

, because they are not variables.

By default, `join`

includes all variables from
`A`

.

`'RightVariables'`

— Variables from `B`

to include in `C`

positive integer | vector of positive integers | character vector | cell array of character vectors | string array | logical vector

Variables from `B`

to include in
`C`

, specified as the comma-separated pair consisting
of `'RightVariables'`

and a positive integer, vector of
positive integers, character vector, cell array of character vectors,
string array, or logical vector.

You can use `'RightVariables'`

to include or exclude
key variables, as well as nonkey variables, from `C`

.
However, you cannot include row names or row times from
`B`

, because they are not variables.

By default, `join`

includes all variables from
`B`

except the key variables.

`'KeepOneCopy'`

— Variables for which `join`

retains only the copy from `A`

character vector | cell array of character vectors | string array

Variables for which `join`

retains only the copy from
`A`

, specified as the comma-separated pair
consisting of `'KeepOneCopy'`

and a character vector,
cell array of character vectors, or string array that specifies variable
names.

Key variables appear once in `C`

, but if nonkey
variables with identical names occur in `A`

and
`B`

, then `join`

retains both
copies in `C`

by default. Use the
`'KeepOneCopy'`

name-value pair to retain only the
copy from `A`

.

**Example: **`'KeepOneCopy',Var2`

keeps only the copy from
`A`

of the nonkey variable
`Var2`

.

`C`

— Merged data from `A`

and `B`

table | timetable

Merged data from `A`

and `B`

, returned
as a table or a timetable. The table, `C`

, contains one row
for each row in `A`

, appearing in the same order.

`join`

creates `C`

by horizontally
concatenating `A(:,LeftVars)`

and
`B(ib,RightVars)`

. By default,
`LeftVars`

is all the variables of
`A`

, and `RightVars`

is all the nonkey
variables from `B`

. Otherwise, `LeftVars`

consists of the variables specified by the
`'LeftVariables'`

name-value pair argument, and
`RightVars`

consists of the variables specified by the
`'RightVariables'`

name-value pair argument.

If `A`

and `B`

contain nonkey variables
with the same name, `join`

adds a unique suffix to the
corresponding variable names in `C`

, unless you specify the
`'KeepOneCopy'`

name-value pair argument.

If `A`

is a table, then `C`

is also a
table. If `A`

is a timetable and `B`

is
either a timetable or a table, then `C`

is a
timetable.

You can store additional metadata in `C`

, such as
descriptions, variable units, variable names, and row names. For more
information, see the Properties sections of `table`

or `timetable`

.

`ib`

— Index to `B`

column vector

Index to `B`

, returned as a column vector. Each element
of `ib`

identifies the row in `B`

that
corresponds to that row in the output table or timetable,
`C`

.

Variable used to match and combine data between input tables
`A`

and `B`

.

Entry in a key variable of `A`

.

The `join`

function first finds one or more key variables. Then,
`join`

uses the key variables to find the row in input table
`B`

that matches each row in input table `A`

, and
combines those rows to create a row in output table `C`

.

If there is a one-to-one mapping between key values in

`A`

and`B`

, then`join`

sorts the data in`B`

and appends it to table`A`

.If there is a many-to-one mapping between key values in

`A`

and`B`

, then`join`

sorts and repeats the data in`B`

before appending it to table`A`

.If there is data in a key variable of

`B`

that does not map to a key value in`A`

, then`join`

does not include that data in the output table,`C`

.

Calculate with arrays that have more rows than fit in memory.

Usage notes and limitations:

To join a tall timetable and a tall table, the timetable must be the first input to

`join`

.

For more information, see Tall Arrays.

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