Torkel ÖdegaardandRyan McKinley
25813db334
* RowsToFields: Fix issue with field names that are numbers * Only add the index accessor if field name does not conflict with it * fix lint Co-authored-by: Ryan McKinley <ryantxu@gmail.com>
102 lines
2.7 KiB
TypeScript
102 lines
2.7 KiB
TypeScript
import { DataFrame } from '../types/dataFrame';
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import { DisplayProcessor } from '../types';
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import { FunctionalVector } from '../vector/FunctionalVector';
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/**
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* This abstraction will present the contents of a DataFrame as if
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* it were a well typed javascript object Vector.
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*
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* @remarks
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* The {@link DataFrameView.get} is optimized for use in a loop and will return same object.
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* See function for more details.
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*
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* @typeParam T - Type of object stored in the DataFrame.
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* @beta
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*/
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export class DataFrameView<T = any> extends FunctionalVector<T> {
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private index = 0;
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private obj: T;
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constructor(private data: DataFrame) {
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super();
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const obj = ({} as unknown) as T;
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for (let i = 0; i < data.fields.length; i++) {
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const field = data.fields[i];
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const getter = () => field.values.get(this.index);
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if (!(obj as any).hasOwnProperty(field.name)) {
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Object.defineProperty(obj, field.name, {
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enumerable: true, // Shows up as enumerable property
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get: getter,
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});
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}
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if (!(obj as any).hasOwnProperty(i.toString())) {
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Object.defineProperty(obj, i, {
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enumerable: false, // Don't enumerate array index
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get: getter,
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});
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}
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}
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this.obj = obj;
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}
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get dataFrame() {
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return this.data;
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}
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get length() {
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return this.data.length;
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}
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/**
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* Helper function to return the {@link DisplayProcessor} for a given field column.
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* @param colIndex - the field column index for the data frame.
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*/
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getFieldDisplayProcessor(colIndex: number): DisplayProcessor | undefined {
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if (!this.dataFrame || !this.dataFrame.fields) {
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return undefined;
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}
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const field = this.dataFrame.fields[colIndex];
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if (!field || !field.display) {
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return undefined;
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}
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return field.display;
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}
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/**
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* The contents of the object returned from this function
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* are optimized for use in a loop. All calls return the same object
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* but the index has changed.
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*
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* @example
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* ```typescript
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* // `first`, `second` and `third` will all point to the same contents at index 2:
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* const first = view.get(0);
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* const second = view.get(1);
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* const third = view.get(2);
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*
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* // If you need three different objects, consider something like:
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* const first = { ...view.get(0) };
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* const second = { ...view.get(1) };
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* const third = { ...view.get(2) };
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* ```
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* @param idx - The index of the object you currently are inspecting
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*/
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get(idx: number) {
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this.index = idx;
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return this.obj;
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}
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toArray(): T[] {
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return new Array(this.data.length)
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.fill(0) // Needs to make a full copy
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.map((_, i) => ({ ...this.get(i) }));
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}
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}
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