mirror of
https://github.com/acamarata/nrel-spa-dart.git
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69 lines
1.8 KiB
Markdown
69 lines
1.8 KiB
Markdown
# Quickstart
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## Install
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Add to `pubspec.yaml`:
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```yaml
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dependencies:
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nrel_spa: ^1.0.1
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```
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Run `dart pub get`.
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## First Call
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```dart
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import 'package:nrel_spa/nrel_spa.dart';
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void main() {
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final result = getSpa(
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DateTime.utc(2024, 3, 15, 17, 0, 0),
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40.7128, // latitude (New York)
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-74.0060, // longitude
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-5.0, // UTC offset (EST)
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);
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print('Solar zenith: ${result.zenith.toStringAsFixed(4)}°');
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print('Solar azimuth: ${result.azimuth.toStringAsFixed(4)}°');
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print('Sunrise: ${result.sunrise.toStringAsFixed(4)} h');
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print('Solar noon: ${result.solarNoon.toStringAsFixed(4)} h');
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print('Sunset: ${result.sunset.toStringAsFixed(4)} h');
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}
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```
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## Reading Results
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`getSpa` returns an `SpaResult`:
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| Field | Type | Description |
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| --- | --- | --- |
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| `zenith` | `double` | Solar zenith angle (degrees) |
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| `azimuth` | `double` | Solar azimuth angle (degrees from north) |
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| `sunrise` | `double` | Sunrise time (decimal hours, UTC) |
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| `solarNoon` | `double` | Solar noon time (decimal hours, UTC) |
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| `sunset` | `double` | Sunset time (decimal hours, UTC) |
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| `angles` | `List<AngleResult>` | Rise/set times for custom zenith angles |
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## DateTime Input
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Always pass UTC `DateTime` values. The `timezone` parameter shifts the output times to local time.
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```dart
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// Convert local DateTime to UTC before passing
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final local = DateTime(2024, 3, 15, 12, 0, 0);
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final utc = local.toUtc();
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final result = getSpa(utc, lat, lng, utcOffset);
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```
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## Null Results for Sunrise/Sunset
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At polar latitudes or in summer/winter extremes, sunrise or sunset may not occur. In those cases, `result.sunrise` and `result.sunset` return `double.nan`. Always check before displaying:
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```dart
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if (!result.sunrise.isNaN) {
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print('Sunrise: ${result.sunrise}');
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} else {
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print('No sunrise today.');
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}
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```
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