**Contents:**

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

**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.

**NOTE: **This function applies to a sample of the entire population. More information is below.

For more information on how the platform calculates standard deviation, see STDEV 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

stdevsampif(testScores, testScores > 0)

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

column when the `testScores`

value is greater than 0.

## Syntax and Arguments

stdevsampif(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

`STDEVSAMP`

- computes standard deviation using the sample method. See STDEVSAMP Function.`VARSAMP`

- computes variance using the sample method. See VARSAMP Function.`STDEVSAMPIF`

- computes standard deviation based on a condition and using the sample method. See STDEVSAMPIF Function.`VARSAMPIF`

- computes standard deviation based on a condition and using the sample method. See VARSAMPIF Function.

**Source:**

Students took tests on three consecutive Saturdays:

Student | Date | Score |
---|---|---|

Andrew | 11/9/19 | 81 |

Bella | 11/9/19 | 84 |

Christina | 11/9/19 | 79 |

David | 11/9/19 | 64 |

Ellen | 11/9/19 | 61 |

Fred | 11/9/19 | 63 |

Andrew | 11/16/19 | 73 |

Bella | 11/16/19 | 88 |

Christina | 11/16/19 | 78 |

David | 11/16/19 | 67 |

Ellen | 11/16/19 | 87 |

Fred | 11/16/19 | 90 |

Andrew | 11/23/19 | 76 |

Bella | 11/23/19 | 93 |

Christina | 11/23/19 | 81 |

David | 11/23/19 | 97 |

Ellen | 11/23/19 | 97 |

Fred | 11/23/19 | 91 |

**Transformation:**

You can use the following transformations to calculate standard deviation and variance across all dates using the sample method. Each computation has been rounded to three digits.

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

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(stdevsamp(Score), 3)` |

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

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

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(varsamp(Score), 3)` |

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

You can use the following to limit the previous statistical computations to the last two Saturdays of testing:

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

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(stdevsampif(Score, Date != '11\/9\/2019'), 3)` |

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

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

Parameter: Formula type | `Single row formula` |

Parameter: Formula | `round(varsampif(Score, Date != '11\/9\/2019'), 3)` |

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

**Results:**

Student | Date | Score | varSampIf | stdevSampIf | varSamp | stdevSamp |
---|---|---|---|---|---|---|

Andrew | 11/9/19 | 81 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/9/19 | 84 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/9/19 | 79 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/9/19 | 64 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/9/19 | 61 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/9/19 | 63 | 94.515 | 9.722 | 131.673 | 11.475 |

Andrew | 11/16/19 | 73 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/16/19 | 88 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/16/19 | 78 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/16/19 | 67 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/16/19 | 87 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/16/19 | 90 | 94.515 | 9.722 | 131.673 | 11.475 |

Andrew | 11/23/19 | 76 | 94.515 | 9.722 | 131.673 | 11.475 |

Bella | 11/23/19 | 93 | 94.515 | 9.722 | 131.673 | 11.475 |

Christina | 11/23/19 | 81 | 94.515 | 9.722 | 131.673 | 11.475 |

David | 11/23/19 | 97 | 94.515 | 9.722 | 131.673 | 11.475 |

Ellen | 11/23/19 | 97 | 94.515 | 9.722 | 131.673 | 11.475 |

Fred | 11/23/19 | 91 | 94.515 | 9.722 | 131.673 | 11.475 |

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