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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.

Relevant terms:

Term Description
Population Population statistical functions are computed from all possible values. See https://en.wikipedia.org/wiki/Statistical_population.
Sample

Sample-based statistical functions are computed from a subset or sample of all values. See https://en.wikipedia.org/wiki/Sampling_(statistics).

These function names include `SAMP` in their name.

NOTE: Statistical sampling has no relationship to the samples taken within the product. When statistical functions are computed during job execution, they are applied across the entire dataset. Sample method calculations are computed at that time.

• 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 &gt; 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]

ArgumentRequired?Data TypeDescription
col_refYstringReference to the column you wish to evaluate.
test_expressionYstringExpression that is evaluated. Must resolve to `true` or `false`

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 TypeExample Value
YesString 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 TypeExample Value
YesString expression that evaluates to `true` or `false````(LastName == 'Mouse' && FirstName == 'Mickey') ```

## Examples

### Example - Conditional Calculation Functions

This example illustrates how to use the conditional calculation functions.

Functions:

ItemDescription
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:

datecityraintempwind
1/23/17Valleyville0.0012.86.7
1/23/17Center Town0.319.45.3
1/23/17Magic Mountain0.000.07.3
1/24/17Valleyville0.2517.23.3
1/24/17Center Town0.541.17.6
1/24/17Magic Mountain0.325.08.8
1/25/17Valleyville0.023.36.8
1/25/17Center Town0.833.35.1
1/25/17Magic Mountain0.59-1.76.4
1/26/17Valleyville1.0815.04.2
1/26/17Center Town0.966.17.6
1/26/17Magic Mountain0.77-3.93.0
1/27/17Valleyville1.007.22.8
1/27/17Center Town1.3220.00.2
1/27/17Magic Mountain0.775.65.2
1/28/17Valleyville0.12-6.15.1
1/28/17Center Town0.145.04.9
1/28/17Magic Mountain1.501.10.4
1/29/17Valleyville0.3613.37.3
1/29/17Center Town0.756.19.0
1/29/17Magic Mountain0.603.36.0

Transformation:

The following computes average temperature for rainy days by city:

Transformation Name `New formula` `Single row formula` `AVERAGEIF(temp, rain > 0)` `city` `'avgTempWRain'`

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

Transformation Name `New formula` `Single row formula` `MAXIF(wind,temp < 0)` `city` `'maxWindSubZero'`

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

Transformation Name `New formula` `Single row formula` `MINIF(temp,wind<5)` `city` `'minTempWind5'`

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

Transformation Name `New formula` `Single row formula` `VARIF(temp,rain >0)` `city` `'varTempWRain'`

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

Transformation Name `New formula` `Single row formula` `STDEVIF(rain,city=='Center Town')` `city` `'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` `stDevRainCenterTown,maxWindSubZero` `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` `varTempWRain,avgTempWRain,minTempWind5` `numformat(\$col,'##.#')`

Results:

datecityraintempwindavgTempWRainmaxWindSubZerominTempWind5varTempWRainstDevRainCT
1/23/17Valleyville0.0012.86.78.35.17.263.80.37
1/23/17Center Town0.319.45.37.3 532.60.37
1/23/17Magic Mountain0.000.07.31.66.43-3.9120.37
1/24/17Valleyville0.2517.23.38.35.17.263.80.37
1/24/17Center Town0.541.17.67.3 532.60.37
1/24/17Magic Mountain0.325.08.81.66.43-3.9120.37
1/25/17Valleyville0.023.36.88.35.17.263.80.37
1/25/17Center Town0.833.35.17.3 532.60.37
1/25/17Magic Mountain0.59-1.76.41.66.43-3.9120.37
1/26/17Valleyville1.0815.04.28.35.17.263.80.37
1/26/17Center Town0.966.17.67.3 532.60.37
1/26/17Magic Mountain0.77-3.93.01.66.43-3.9120.37
1/27/17Valleyville1.007.22.88.35.17.263.80.37
1/27/17Center Town1.3220.00.27.3 532.60.37
1/27/17Magic Mountain0.775.65.21.66.43-3.9120.37
1/28/17Valleyville0.12-6.15.18.35.17.263.80.37
1/28/17Center Town0.145.04.97.3 532.60.37
1/28/17Magic Mountain1.501.10.41.66.43-3.9120.37
1/29/17Valleyville0.3613.37.38.35.17.263.80.37
1/29/17Center Town0.756.19.07.3 532.60.37
1/29/17Magic Mountain0.603.36.01.66.43-3.9120.37

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