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Transformation: Added variance and standard deviation (#48844)

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* Transformation: Added variance and standard deviation for sample and population. Modified mean calculation approach

* Transformation: Removed existing mean calculation

* Transformation: Added testcases for variance and Standard deviation

* Update docs/sources/panels/calculation-types.md

Co-authored-by: brendamuir <100768211+brendamuir@users.noreply.github.com>

Co-authored-by: brendamuir <100768211+brendamuir@users.noreply.github.com>
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selvavm 2022-05-12 05:46:41 +05:30 committed by GitHub
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commit 906484b809
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3 changed files with 88 additions and 21 deletions
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8
docs/sources/panels/calculation-types.md
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@ -6,10 +6,10 @@ weight = 1100
# Reference: Calculation types
Refer to the following list of calculations you can perform in Grafana. You can find these calculations in the **Transform** tab and in the bar gauge, gauge, and stat visualizations.
You can perform the following calculations in Grafana. Navigate to the **Transform** tab and in the bar gauge, gauge, and stat visualizations.
| Calculation | Description |
| :----------------- | :-------------------------------------------------------- |
| :------------------------------ | :---------------------------------------------------------------- |
| All nulls | True when all values are null |
| All zeros | True when all values are 0 |
| Change count | Number of times the field's value changes |
@ -21,6 +21,10 @@ Refer to the following list of calculations you can perform in Grafana. You can
| First (not null) | First, not null value in a field |
| Max | Maximum value of a field |
| Mean | Mean value of all values in a field |
| Variance (Population) | Variance (based on population) of all values in a field |
| Standard deviation (Population) | Standard deviation (based on population) of all values in a field |
| Variance (Sample) | Variance (based on sample) of all values in a field |
| Standard deviation (Sample) | Standard deviation (based on sample) of all values in a field |
| Min | Minimum value of a field |
| Min (above zero) | Minimum, positive value of a field |
| Range | Difference between maximum and minimum values of a field |

15
packages/grafana-data/src/transformations/fieldReducer.test.ts
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@ -56,13 +56,26 @@ describe('Stats Calculators', () => {
it('should calculate basic stats', () => {
const stats = reduceField({
field: basicTable.fields[0],
reducers: ['first', 'last', 'mean', 'count'],
reducers: [
'first',
'last',
'mean',
'count',
'Variance (Population)',
'Variance (Sample)',
'Standard deviation (Population)',
'Standard deviation (Sample)',
],
});
expect(stats.first).toEqual(10);
expect(stats.last).toEqual(20);
expect(stats.mean).toEqual(15);
expect(stats.count).toEqual(2);
expect(stats.variancePopulation).toEqual(25);
expect(stats.varianceSample).toEqual(50);
expect(stats.stddevPopulation).toEqual(5);
expect(stats.stddevSample).toBeCloseTo(7.0710678, 5);
});
it('should support a single stat also', () => {

52
packages/grafana-data/src/transformations/fieldReducer.ts
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@ -10,6 +10,10 @@ export enum ReducerID {
min = 'min',
logmin = 'logmin',
mean = 'mean',
variancePopulation = 'variancePopulation',
stddevPopulation = 'stddevPopulation',
varianceSample = 'varianceSample',
stddevSample = 'stddevSample',
last = 'last',
first = 'first',
count = 'count',
@ -152,6 +156,30 @@ export const fieldReducers = new Registry<FieldReducerInfo>(() => [
{ id: ReducerID.min, name: 'Min', description: 'Minimum Value', standard: true },
{ id: ReducerID.max, name: 'Max', description: 'Maximum Value', standard: true },
{ id: ReducerID.mean, name: 'Mean', description: 'Average Value', standard: true, aliasIds: ['avg'] },
{
id: ReducerID.variancePopulation,
name: 'Variance (Population)',
description: 'Variance (based on population) of all values in a field',
standard: true,
},
{
id: ReducerID.stddevPopulation,
name: 'Standard deviation (Population)',
description: 'Standard deviation (based on population) of all values in a field',
standard: true,
},
{
id: ReducerID.varianceSample,
name: 'Variance (Sample)',
description: 'Variance (based on sample) of all values in a field',
standard: true,
},
{
id: ReducerID.stddevSample,
name: 'Standard deviation (Sample)',
description: 'Standard deviation (based on sample) of all values in a field',
standard: true,
},
{
id: ReducerID.sum,
name: 'Total',
@ -256,6 +284,10 @@ export function doStandardCalcs(field: Field, ignoreNulls: boolean, nullAsZero:
min: Number.MAX_VALUE,
logmin: Number.MAX_VALUE,
mean: null,
variancePopulation: null,
stddevPopulation: null,
varianceSample: null,
stddevSample: null,
last: null,
first: null,
lastNotNull: null,
@ -274,6 +306,8 @@ export function doStandardCalcs(field: Field, ignoreNulls: boolean, nullAsZero:
previousDeltaUp: true,
} as FieldCalcs;
let squareSum = 0;
const data = field.values;
calcs.count = data.length;
@ -343,6 +377,10 @@ export function doStandardCalcs(field: Field, ignoreNulls: boolean, nullAsZero:
if (currentValue < calcs.logmin && currentValue > 0) {
calcs.logmin = currentValue;
}
let _oldMean = calcs.mean;
calcs.mean += (currentValue - _oldMean) / calcs.nonNullCount;
squareSum += (currentValue - _oldMean) * (currentValue - calcs.mean);
}
if (currentValue !== 0) {
@ -366,7 +404,19 @@ export function doStandardCalcs(field: Field, ignoreNulls: boolean, nullAsZero:
}
if (calcs.nonNullCount > 0) {
calcs.mean = calcs.sum! / calcs.nonNullCount;
calcs.variancePopulation = squareSum / calcs.nonNullCount;
}
if (calcs.nonNullCount > 0) {
calcs.stddevPopulation = Math.sqrt(calcs.variancePopulation);
}
if (calcs.nonNullCount > 0) {
calcs.varianceSample = squareSum / (calcs.nonNullCount - 1);
}
if (calcs.nonNullCount > 0) {
calcs.stddevSample = Math.sqrt(calcs.varianceSample);
}
if (calcs.allIsNull) {