# Stub (Row Labels)
The **Stub** is a structural component that gives your table a left-hand column of row identifiers. Rather than treating row labels as just another data column, the stub elevates them to a distinct organizational role. This section covers how to create a stub, label it with a stubhead, and organize rows into logical groups.
# Overview
The **Stub** component of a table is the area to the left that typically contains *row labels* and may also contain *row group labels*. Those subparts can be grouped in a sequence of *row groups*. The **Stub Head** provides a location for a label that describes the **Stub** (and could also be used to describe the column labels). The **Stub** is optional since there are cases where a **Stub** wouldn't be useful (the display tables presented in the previous section looked just fine without a **Stub**).
# Row names
An easy way to generate a **Stub** part is by specifying a stub column in the [GT()](../reference/GT.md#great_tables.GT) class with the `rowname_col=` argument. This will signal to **Great Tables** that the named column should be used as the stub, using the contents of that column to make *row labels*. Let's add a stub with our `islands` dataset by using `rowname_col=` in the call to [GT](../reference/GT.md#great_tables.GT):
``` python
from great_tables import GT
from great_tables.data import islands
islands_mini = islands.head(10)
GT(islands_mini).tab_stub(rowname_col="name")
```
| | size |
|--------------|-------|
| Africa | 11506 |
| Antarctica | 5500 |
| Asia | 16988 |
| Australia | 2968 |
| Axel Heiberg | 16 |
| Baffin | 184 |
| Banks | 23 |
| Borneo | 280 |
| Britain | 84 |
| Celebes | 73 |
Notice that the landmass names are now placed to the left? That's the **Stub**. Notably, there is a prominent border to the right of it but there's no label above the **Stub**. We can change this and apply what's known as a *stubhead label* through use of the [tab_stubhead()](../reference/GT.tab_stubhead.md#great_tables.GT.tab_stubhead) method:
``` python
(
GT(islands_mini)
.tab_stub(rowname_col="name")
.tab_stubhead(label="landmass")
)
```
| landmass | size |
|--------------|-------|
| Africa | 11506 |
| Antarctica | 5500 |
| Asia | 16988 |
| Australia | 2968 |
| Axel Heiberg | 16 |
| Baffin | 184 |
| Banks | 23 |
| Borneo | 280 |
| Britain | 84 |
| Celebes | 73 |
A very important thing to note here is that the table now has one column. Before, when there was no **Stub**, two columns were present (with the **Column Labels** of `"name"` and `"size"`) but now column number `1` (the only column remaining) is `size`.
# Row groups
Let's incorporate row groups into the display table. This divides rows into groups, creating *row groups*, and results in a display of a *row group labels* right above the each group. This can be easily done with a table containing row labels and the key is to use the `groupname_col=` argument of the [GT](../reference/GT.md#great_tables.GT) class. Here we will create three row groups (with row group labels `"continent"`, `"country"`, and `"subregion"`) to have a grouping of rows.
``` python
island_groups = islands.head(10).assign(group = ["subregion"] * 2 + ["country"] * 2 + ["continent"] * 6)
(
GT(island_groups)
.tab_stub(rowname_col="name", groupname_col="group")
.tab_stubhead(label="landmass")
)
```
| landmass |
size |
| subregion |
| Africa |
11506 |
| Antarctica |
5500 |
| country |
| Asia |
16988 |
| Australia |
2968 |
| continent |
| Axel Heiberg |
16 |
| Baffin |
184 |
| Banks |
23 |
| Borneo |
280 |
| Britain |
84 |
| Celebes |
73 |
The table now groups its rows by continent, country, and subregion, with labels appearing above each group. Row groups make it much easier for readers to scan and compare related entries.
# GT convenience arguments
Rather than using the [tab_stub()](../reference/GT.tab_stub.md#great_tables.GT.tab_stub) method, the `GT(rowname_col=..., groupname_col=...)` arguments provide a quick way to specify row names and groups.
``` python
GT(island_groups, rowname_col="name", groupname_col="group")
```
|
size |
| subregion |
| Africa |
11506 |
| Antarctica |
5500 |
| country |
| Asia |
16988 |
| Australia |
2968 |
| continent |
| Axel Heiberg |
16 |
| Baffin |
184 |
| Banks |
23 |
| Borneo |
280 |
| Britain |
84 |
| Celebes |
73 |
The stub provides a clear organizational framework for your data by separating identifiers from values. Whether you simply need named rows or a fully grouped hierarchy, the combination of `rowname_col=`, `groupname_col=`, and [tab_stubhead()](../reference/GT.tab_stubhead.md#great_tables.GT.tab_stubhead) gives you precise control over how readers navigate your table.