[//]: # (title: update)

<!---IMPORT org.jetbrains.kotlinx.dataframe.samples.api.Modify-->

Returns [`DataFrame`](DataFrame.md) with changed values in some cells. Column types can not be changed.

```text
update { columns }
    [.where { rowCondition } ]
    [.at(rowIndices) ] 
     .with { rowExpression } | .notNull { rowExpression } | .perCol { colExpression } | .perRowCol { rowColExpression } | .withNull() | .withZero() | .asFrame { frameExpression } 

rowCondition: DataRow.(OldValue) -> Boolean
rowExpression: DataRow.(OldValue) -> NewValue
colExpression: DataColumn.(DataColumn) -> NewValue
rowColExpression: (DataRow, DataColumn) -> NewValue
frameExpression: DataFrame.(DataFrame) -> DataFrame
```

**Related operations**: [](updateConvert.md)

See [column selectors](ColumnSelectors.md) for how to select the columns for this operation and
[row expressions](DataRow.md#row-expressions) for how to specify the new values.

<!---FUN update-->

```kotlin
df.update { age }.with { it * 2 }
df.update { colsAtAnyDepth().colsOf<String>() }.with { it.uppercase() }
df.update { weight }.at(1..4).notNull { it / 2 }
df.update { name.lastName and age }.at(1, 3, 4).withNull()
```

<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.update.html" width="100%"/>
<!---END-->

Update with constant value:

<!---FUN updateWithConst-->

```kotlin
df.update { city }.where { name.firstName == "Alice" }.with { "Paris" }
```

<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.updateWithConst.html" width="100%"/>
<!---END-->

Update with value depending on row:

<!---FUN updateWith-->

```kotlin
df.update { city }.with { name.firstName + " from " + it }
```

<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.updateWith.html" width="100%"/>
<!---END-->

Update with value depending on column:

<!---FUN updatePerColumn-->

```kotlin
df.update { colsOf<Number?>() }.perCol { mean(skipNaN = true) }
```

<!---END-->

Update with value depending on row and column:

<!---FUN updatePerRowCol-->

```kotlin
df.update { colsOf<String?>() }.perRowCol { row, col -> col.name() + ": " + row.index() }
```

<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.updatePerRowCol.html" width="100%"/>
<!---END-->

Update [ColumnGroup](DataColumn.md#columngroup) as [DataFrame](DataFrame.md):

<!---FUN updateAsFrame-->

```kotlin
df.update { name }.asFrame { select { lastName } }
```

<inline-frame src="resources/org.jetbrains.kotlinx.dataframe.samples.api.Modify.updateAsFrame.html" width="100%"/>
<!---END-->