pages/_posts/2024-01-27-vega-lite.md
Tao Deng a29e24a46b
add last updated date to posts (#2341)
This PR is related to #2309. I added an optional `last_updated` field.
This new field represents the timestamp for when the post was last
updated. Consequently, the existing `date` metadata should now be
interpreted as the creation date of the post.

The formatting for displaying these dates has been standardized as
follows:

```text
Created: July 11, 2023   |   Last Updated: April 14, 2024
```

For a practical implementation example, please refer to [this
post](https://torydeng.github.io/blog/2023/deploying-server/) on my
website, where I have applied these changes.

---

Any feedback is wellcome.
2024-04-24 12:19:36 -03:00

2.7 KiB

layout title date last_updated description tags categories chart
post a post with vega lite 2024-01-27 00:20:00 2024-04-14 04:30:00 this is what included vega lite code could look like formatting charts sample-posts
vega_lite
true

This is an example post with some vega lite code.

```vega_lite
{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "A dot plot showing each movie in the database, and the difference from the average movie rating. The display is sorted by year to visualize everything in sequential order. The graph is for all Movies before 2019.",
  "data": {
    "url": "https://raw.githubusercontent.com/vega/vega/main/docs/data/movies.json"
  },
  "transform": [
    {"filter": "datum['IMDB Rating'] != null"},
    {"filter": {"timeUnit": "year", "field": "Release Date", "range": [null, 2019]}},
    {
      "joinaggregate": [{
        "op": "mean",
        "field": "IMDB Rating",
        "as": "AverageRating"
      }]
    },
    {
      "calculate": "datum['IMDB Rating'] - datum.AverageRating",
      "as": "RatingDelta"
    }
  ],
  "mark": "point",
  "encoding": {
    "x": {
      "field": "Release Date",
      "type": "temporal"
    },
    "y": {
      "field": "RatingDelta",
      "type": "quantitative",
      "title": "Rating Delta"
    },
    "color": {
      "field": "RatingDelta",
      "type": "quantitative",
      "scale": {"domainMid": 0},
      "title": "Rating Delta"
    }
  }
}
```

Which generates:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "description": "A dot plot showing each movie in the database, and the difference from the average movie rating. The display is sorted by year to visualize everything in sequential order. The graph is for all Movies before 2019.",
  "data": {
    "url": "https://raw.githubusercontent.com/vega/vega/main/docs/data/movies.json"
  },
  "transform": [
    {"filter": "datum['IMDB Rating'] != null"},
    {"filter": {"timeUnit": "year", "field": "Release Date", "range": [null, 2019]}},
    {
      "joinaggregate": [{
        "op": "mean",
        "field": "IMDB Rating",
        "as": "AverageRating"
      }]
    },
    {
      "calculate": "datum['IMDB Rating'] - datum.AverageRating",
      "as": "RatingDelta"
    }
  ],
  "mark": "point",
  "encoding": {
    "x": {
      "field": "Release Date",
      "type": "temporal"
    },
    "y": {
      "field": "RatingDelta",
      "type": "quantitative",
      "title": "Rating Delta"
    },
    "color": {
      "field": "RatingDelta",
      "type": "quantitative",
      "scale": {"domainMid": 0},
      "title": "Rating Delta"
    }
  }
}

This plot supports both light and dark themes.