Computes the standard deviation across all column values of Integer or Decimal type.
The standard deviation of a set of values attempts to measure the spread in values around the mean and is used to measure confidence in statistical results. A standard deviation of zero means that all values are the same, and a small standard deviation means that the values are closely bunched together. A high value for standard deviation indicates that the numbers are spread out widely. Standard deviation is always a positive value.
- If a row contains a missing or null value, it is not factored into the calculation.
- If no numeric values are detected in the input column, the function returns
0
.
This function is calculated across the entire population.
- For more information on a sampled version of this function, see STDEVSAMP Function.
The square of standard deviation is variance. See VAR Function.
For a version of this function computed over a rolling window of rows, see ROLLINGSTDEV 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
stdev(myRating)
Output: Returns the standard deviation of the values from the myRating
column.
Syntax and Arguments
stdev(function_col_ref) [group:group_col_ref] [limit:limit_count]
Argument | Required? | Data Type | Description |
---|---|---|---|
function_col_ref | Y | string | Name of column to which to apply the function |
For more information on the group
and limit
parameters, see Pivot Transform.
For more information on syntax standards, see Language Documentation Syntax Notes.
function_col_ref
Name of the column the values of which you want to calculate the variance. Column must contain Integer or Decimal values.
- Literal values are not supported as inputs.
- Multiple columns and wildcards are not supported.
Usage Notes:
Required? | Data Type | Example Value |
---|---|---|
Yes | String (column reference) | myValues |
Tip: For additional examples, see Common Tasks.
Examples
Source: Students took a test and recorded the following scores. You want to perform some statistical analysis on them: Transformation: You can use the following transformations to calculate the average (mean), minimum, and maximum scores: To apply statistical functions to your data, you can use the For each score, you can now calculate the variation of each one from the average, using the following: Now, you want to apply grades based on a formula: You can build the following transformation using the For more information, see IF Function. To clean up the content, you might want to apply some formatting to the score columns. The following reformats the Results: 87.00000000000001Student Score Anna 84 Ben 71 Caleb 76 Danielle 87 Evan 85 Faith 92 Gabe 85 Hannah 99 Ian 73 Jane 68
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
AVERAGE(Score)
Parameter: New column name
'avgScore'
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
MIN(Score)
Parameter: New column name
'minScore'
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
MAX(Score)
Parameter: New column name
'maxScore'
VAR
and STDEV
functions, which can be used as the basis for other statistical calculations.
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
VAR(Score)
Parameter: New column name
var_Score
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
STDEV(Score)
Parameter: New column name
stdev_Score
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
((Score - avg_Score) / stdev_Score)
Parameter: New column name
'stDevs'
Grade standard deviations from avg (stDevs) A stDevs > 1 B stDevs > 0.5 C -1 <= stDevs <= 0.5 D stDevs < -1 F stDevs < -2 IF
function to calculate grades.
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
IF((stDevs > 1),'A',IF((stDevs < -2),'F',IF((stDevs < -1),'D',IF((stDevs > 0.5),'B','C'))))
stdev_Score
and stDevs
columns to display two decimal places:
Transformation Name
Edit column with formula
Parameter: Columns
stdev_Score
Parameter: Formula
NUMFORMAT(stdev_Score, '##.00')
Transformation Name
Edit column with formula
Parameter: Columns
stDevs
Parameter: Formula
NUMFORMAT(stDevs, '##.00')
Transformation Name
New formula
Parameter: Formula type
Single row formula
Parameter: Formula
MODE(Score)
Parameter: New column name
'modeScore'
Student Score modeScore avgScore minScore maxScore var_Score stdev_Score stDevs Grade Anna 84 85 82 68 99 9.33 0.21 C Ben 71 85 82 68 99 87.00000000000001 9.33 -1.18 D Caleb 76 85 82 68 99 87.00000000000001 9.33 -0.64 C Danielle 87 85 82 68 99 87.00000000000001 9.33 0.54 B Evan 85 85 82 68 99 87.00000000000001 9.33 0.32 C Faith 92 85 82 68 99 87.00000000000001 9.33 1.07 A Gabe 85 85 82 68 99 87.00000000000001 9.33 0.32 C Hannah 99 85 82 68 99 87.00000000000001 9.33 1.82 A Ian 73 85 82 68 99 87.00000000000001 9.33 -0.96 C Jane 68 85 82 68 99 87.00000000000001 9.33 -1.50 D
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