Transformations: Show row index as percent in 'Add field from calculation' (#74322)

* show row index as percentage in add field from calc transform

* prettier

* add test + modify docs

* show quantile and add percentage unit default. add explanatory tooltip and docs

* fix test

* set unit percent only on quantile mode

* Change naming to percentile

* Rename to As Percentile

* docs mods

docs/sources/panels-visualizations/query-transform-data/transform-data/index.md

@@ -109,10 +109,11 @@ Use this transformation to add a new field calculated from two other fields. Eac
 - **Mode -** Select a mode:
   - **Reduce row -** Apply selected calculation on each row of selected fields independently.
   - **Binary option -** Apply basic math operation(sum, multiply, etc) on values in a single row from two selected fields.
-  - **Index -** Will insert a field with the row index.
+  - **Row index -** Insert a field with the row index.
 - **Field name -** Select the names of fields you want to use in the calculation for the new field.
 - **Calculation -** If you select **Reduce row** mode, then the **Calculation** field appears. Click in the field to see a list of calculation choices you can use to create the new field. For information about available calculations, refer to [Calculation types][].
 - **Operation -** If you select **Binary option** mode, then the **Operation** fields appear. These fields allow you to do basic math operations on values in a single row from two selected fields. You can also use numerical values for binary operations.
+- **As percentile -** If you select **Row index** mode, then the **As percentile** switch appears. This switch allows you to transform the row index as a percentage of the total number of rows.
 - **Alias -** (Optional) Enter the name of your new field. If you leave this blank, then the field will be named to match the calculation.
 - **Replace all fields -** (Optional) Select this option if you want to hide all other fields and display only your calculated field in the visualization.
 

packages/grafana-data/src/transformations/transformers/calculateField.test.ts

@@ -238,6 +238,34 @@ describe('calculateField transformer w/ timeseries', () => {
     });
   });
 
+  it('can add percentage index field', async () => {
+    const cfg = {
+      id: DataTransformerID.calculateField,
+      options: {
+        mode: CalculateFieldMode.Index,
+        replaceFields: true,
+        index: {
+          asPercentile: true,
+        },
+      },
+    };
+
+    const series = toDataFrame({
+      fields: [
+        { name: 'TheTime', type: FieldType.time, values: [1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000] },
+        { name: 'Field', type: FieldType.number, values: [2, 200, 3, 6, 3, 7, 9, 9] },
+      ],
+    });
+
+    await expect(transformDataFrame([cfg], [series])).toEmitValuesWith((received) => {
+      const data = received[0][0];
+      expect(data.fields.length).toEqual(1);
+      expect(data.fields[0].values[2]).toEqual(0.25);
+      expect(data.fields[0].values[4]).toEqual(0.5);
+      expect(data.fields[0].values[6]).toEqual(0.75);
+    });
+  });
+
   it('uses template variable substituion', async () => {
     const cfg = {
       id: DataTransformerID.calculateField,

packages/grafana-data/src/transformations/transformers/calculateField.ts

@@ -31,6 +31,10 @@ export interface BinaryOptions {
   right: string;
 }
 
+export interface IndexOptions {
+  asPercentile: boolean;
+}
+
 const defaultReduceOptions: ReduceOptions = {
   reducer: ReducerID.sum,
 };
@@ -49,6 +53,7 @@ export interface CalculateFieldTransformerOptions {
   // Only one should be filled
   reduce?: ReduceOptions;
   binary?: BinaryOptions;
+  index?: IndexOptions;
 
   // Remove other fields
   replaceFields?: boolean;
@@ -98,11 +103,19 @@ export const calculateFieldTransformer: DataTransformerInfo<CalculateFieldTransf
           creator = getBinaryCreator(defaults(binaryOptions, defaultBinaryOptions), data);
         } else if (mode === CalculateFieldMode.Index) {
           return data.map((frame) => {
+            const indexArr = [...Array(frame.length).keys()];
+
+            if (options.index?.asPercentile) {
+              for (let i = 0; i < indexArr.length; i++) {
+                indexArr[i] = indexArr[i] / indexArr.length;
+              }
+            }
+
             const f = {
               name: options.alias ?? 'Row',
               type: FieldType.number,
-              values: [...Array(frame.length).keys()],
+              values: indexArr,
-              config: {},
+              config: options.index?.asPercentile ? { unit: 'percentunit' } : {},
             };
             return {
               ...frame,

public/app/features/transformers/editors/CalculateFieldTransformerEditor.tsx

@@ -23,6 +23,7 @@ import {
   CalculateFieldMode,
   CalculateFieldTransformerOptions,
   getNameFromOptions,
+  IndexOptions,
   ReduceOptions,
 } from '@grafana/data/src/transformations/transformers/calculateField';
 import { FilterPill, HorizontalGroup, Input, LegacyForms, Select, StatsPicker } from '@grafana/ui';
@@ -142,6 +143,16 @@ export class CalculateFieldTransformerEditor extends React.PureComponent<
     });
   };
 
+  onToggleRowIndexAsPercentile = () => {
+    const { options } = this.props;
+    this.props.onChange({
+      ...options,
+      index: {
+        asPercentile: !options.index?.asPercentile ?? false,
+      },
+    });
+  };
+
   onModeChanged = (value: SelectableValue<CalculateFieldMode>) => {
     const { options, onChange } = this.props;
     const mode = value.value ?? CalculateFieldMode.BinaryOperation;
@@ -197,6 +208,22 @@ export class CalculateFieldTransformerEditor extends React.PureComponent<
     this.updateReduceOptions({ ...reduce, reducer });
   };
 
+  renderRowIndex(options?: IndexOptions) {
+    return (
+      <>
+        <div className="gf-form-inline">
+          <LegacyForms.Switch
+            label="As percentile"
+            tooltip="Transform the row index as a percentile."
+            labelClass="width-8"
+            checked={!!options?.asPercentile}
+            onChange={this.onToggleRowIndexAsPercentile}
+          />
+        </div>
+      </>
+    );
+  }
+
   renderReduceRow(options?: ReduceOptions) {
     const { names, selected } = this.state;
     options = defaults(options, { reducer: ReducerID.sum });
@@ -353,6 +380,7 @@ export class CalculateFieldTransformerEditor extends React.PureComponent<
         </div>
         {mode === CalculateFieldMode.BinaryOperation && this.renderBinaryOperation(options.binary)}
         {mode === CalculateFieldMode.ReduceRow && this.renderReduceRow(options.reduce)}
+        {mode === CalculateFieldMode.Index && this.renderRowIndex(options.index)}
         <div className="gf-form-inline">
           <div className="gf-form">
             <div className="gf-form-label width-8">Alias</div>