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```{python nbsphinx=hidden}
import pandas as pd
pd.set_option("display.max_rows", 20)
```

## Gather

```{python}
from siuba import _, gather, spread
from siuba.data import mtcars
```

```{python}
costs = pd.DataFrame({
    'id': [1,2],
    'price_x': [.1, .2],
    'price_y': [.4, .5],
    'price_z': [.7, .8]
})

costs
```

```{python}
# selecting each variable manually
costs >> gather('measure', 'value', _.price_x, _.price_y, _.price_z)

# selecting variables using a slice
costs >> gather('measure', 'value', _["price_x":"price_z"])

# selecting by excluding id
costs >> gather('measure', 'value', -_.id)
```

### Spread is the inverse of gather

```{python}

(costs
    >> gather('measure', 'value', -_.id)
    >> spread('measure', 'value')
)
```