**Contents:**

Generates the standard deviation of values by group in a column that meet a specific condition.

**NOTE: **When added to a transform, this function is applied to the sample in the data grid. If you change your sample or run the job, the computed values for this function are updated. Transforms that change the number of rows in subsequent recipe steps do not affect the values computed for this step.

This function is calculated across the entire population.

- For more information on a sampled version of this function, see STDEVSAMPIF Function.

**Wrangle vs. SQL:** This function is part of Wrangle
, a proprietary data transformation language. Wrangle
is not SQL. For more information, see Wrangle Language.

## Basic Usage

stdevif(testScores, testScores > 0)

**Output:** Returns the standard deviation of the `testScores`

column when the `testScores`

value is greater than 0.

## Syntax and Arguments

stdevif(col_ref, test_expression) [group:group_col_ref] [limit:limit_count]

Argument | Required? | Data Type | Description |
---|---|---|---|

col_ref | Y | string | Reference to the column you wish to evaluate. |

test_expression | Y | string | Expression that is evaluated. Must resolve to `true` or `false` |

For more information on syntax standards, see Language Documentation Syntax Notes.

For more information on the `group`

and `limit`

parameters, see Pivot Transform.

### col_ref

Name of the column whose values you wish to use in the calculation. Column must be a numeric (Integer or Decimal) type.

**Usage Notes:**

Required? | Data Type | Example Value |
---|---|---|

Yes | String that corresponds to the name of the column | `myValues` |

### test_expression

This parameter contains the expression to evaluate. This expression must resolve to a Boolean (`true`

or `false`

) value.

**Usage Notes:**

Required? | Data Type | Example Value |
---|---|---|

Yes | String expression that evaluates to `true` or `false` | ```
(LastName == 'Mouse' && FirstName == 'Mickey')
``` |

## Examples

**Tip:** For additional examples, see Common Tasks.

### Example - Conditional Calculation Functions

**Functions**:

Item | Description |
---|---|

AVERAGEIF Function | Generates the average value of rows in each group that meet a specific condition. Generated value is of Decimal type. |

MINIF Function | Generates the minimum value of rows in each group that meet a specific condition. Inputs can be Integer, Decimal, or Datetime. |

MAXIF Function | Generates the maximum value of rows in each group that meet a specific condition. Inputs can be Integer, Decimal, or Datetime. |

VARIF Function | Generates the variance of values by group in a column that meet a specific condition. |

STDEVIF Function | Generates the standard deviation of values by group in a column that meet a specific condition. |

**Source:**

Here is some example weather data:

date | city | rain | temp | wind |
---|---|---|---|---|

1/23/17 | Valleyville | 0.00 | 12.8 | 6.7 |

1/23/17 | Center Town | 0.31 | 9.4 | 5.3 |

1/23/17 | Magic Mountain | 0.00 | 0.0 | 7.3 |

1/24/17 | Valleyville | 0.25 | 17.2 | 3.3 |

1/24/17 | Center Town | 0.54 | 1.1 | 7.6 |

1/24/17 | Magic Mountain | 0.32 | 5.0 | 8.8 |

1/25/17 | Valleyville | 0.02 | 3.3 | 6.8 |

1/25/17 | Center Town | 0.83 | 3.3 | 5.1 |

1/25/17 | Magic Mountain | 0.59 | -1.7 | 6.4 |

1/26/17 | Valleyville | 1.08 | 15.0 | 4.2 |

1/26/17 | Center Town | 0.96 | 6.1 | 7.6 |

1/26/17 | Magic Mountain | 0.77 | -3.9 | 3.0 |

1/27/17 | Valleyville | 1.00 | 7.2 | 2.8 |

1/27/17 | Center Town | 1.32 | 20.0 | 0.2 |

1/27/17 | Magic Mountain | 0.77 | 5.6 | 5.2 |

1/28/17 | Valleyville | 0.12 | -6.1 | 5.1 |

1/28/17 | Center Town | 0.14 | 5.0 | 4.9 |

1/28/17 | Magic Mountain | 1.50 | 1.1 | 0.4 |

1/29/17 | Valleyville | 0.36 | 13.3 | 7.3 |

1/29/17 | Center Town | 0.75 | 6.1 | 9.0 |

1/29/17 | Magic Mountain | 0.60 | 3.3 | 6.0 |

** Transformation:**

The following computes average temperature for rainy days by city:

Transformation Name | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `AVERAGEIF(temp, rain > 0)` |

Parameter: Group rows by | `city` |

Parameter: New column name | `'avgTempWRain'` |

The following computes maximum wind for sub-zero days by city:

Transformation Name | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `MAXIF(wind,temp < 0)` |

Parameter: Group rows by | `city` |

Parameter: New column name | `'maxWindSubZero'` |

This step calculates the minimum temp when the wind is less than 5 mph by city:

Transformation Name | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `MINIF(temp,wind<5)` |

Parameter: Group rows by | `city` |

Parameter: New column name | `'minTempWind5'` |

This step computes the variance in temperature for rainy days by city:

Transformation Name | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `VARIF(temp,rain >0)` |

Parameter: Group rows by | `city` |

Parameter: New column name | `'varTempWRain'` |

The following computes the standard deviation in rainfall for Center Town:

Transformation Name | `New formula` |
---|---|

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `STDEVIF(rain,city=='Center Town')` |

Parameter: Group rows by | `city` |

Parameter: New column name | `'stDevRainCT'` |

You can use the following transforms to format the generated output. Note the `$col`

placeholder value for the multi-column transforms:

Transformation Name | `Edit column with formula` |
---|---|

Parameter: Columns | `stDevRainCenterTown,maxWindSubZero` |

Parameter: Formula | `numformat($col,'##.##')` |

Since the following rely on data that has only one significant digit, you should format them differently:

Transformation Name | `Edit column with formula` |
---|---|

Parameter: Columns | `varTempWRain,avgTempWRain,minTempWind5` |

Parameter: Formula | `numformat($col,'##.#')` |

**Results:**

date | city | rain | temp | wind | avgTempWRain | maxWindSubZero | minTempWind5 | varTempWRain | stDevRainCT |
---|---|---|---|---|---|---|---|---|---|

1/23/17 | Valleyville | 0.00 | 12.8 | 6.7 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/23/17 | Center Town | 0.31 | 9.4 | 5.3 | 7.3 | 5 | 32.6 | 0.37 | |

1/23/17 | Magic Mountain | 0.00 | 0.0 | 7.3 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/24/17 | Valleyville | 0.25 | 17.2 | 3.3 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/24/17 | Center Town | 0.54 | 1.1 | 7.6 | 7.3 | 5 | 32.6 | 0.37 | |

1/24/17 | Magic Mountain | 0.32 | 5.0 | 8.8 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/25/17 | Valleyville | 0.02 | 3.3 | 6.8 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/25/17 | Center Town | 0.83 | 3.3 | 5.1 | 7.3 | 5 | 32.6 | 0.37 | |

1/25/17 | Magic Mountain | 0.59 | -1.7 | 6.4 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/26/17 | Valleyville | 1.08 | 15.0 | 4.2 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/26/17 | Center Town | 0.96 | 6.1 | 7.6 | 7.3 | 5 | 32.6 | 0.37 | |

1/26/17 | Magic Mountain | 0.77 | -3.9 | 3.0 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/27/17 | Valleyville | 1.00 | 7.2 | 2.8 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/27/17 | Center Town | 1.32 | 20.0 | 0.2 | 7.3 | 5 | 32.6 | 0.37 | |

1/27/17 | Magic Mountain | 0.77 | 5.6 | 5.2 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/28/17 | Valleyville | 0.12 | -6.1 | 5.1 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/28/17 | Center Town | 0.14 | 5.0 | 4.9 | 7.3 | 5 | 32.6 | 0.37 | |

1/28/17 | Magic Mountain | 1.50 | 1.1 | 0.4 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

1/29/17 | Valleyville | 0.36 | 13.3 | 7.3 | 8.3 | 5.1 | 7.2 | 63.8 | 0.37 |

1/29/17 | Center Town | 0.75 | 6.1 | 9.0 | 7.3 | 5 | 32.6 | 0.37 | |

1/29/17 | Magic Mountain | 0.60 | 3.3 | 6.0 | 1.6 | 6.43 | -3.9 | 12 | 0.37 |

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