Extension:Graph/Demo/CategoryPie
From Linux Web Expert
<graph> {
"version": 2,
"width": 300,
"height": 300,
"data": [
{
// Data is retrieved from the MediaWiki API. By default it uses current wiki's "Extension by category"
"name": "table",
"url": "wikiapi:///?generator=categorymembers&gcmtitle=Category:Extensions+by+category&gcmtype=subcat&action=query&gcmlimit=max&prop=categoryinfo&formatversion=2&format=json",
// We are only interested in the content of query.pages subelement.
"format": {"property": "query.pages","type": "json"},
"transform": [
// sort in descending order using category size as the sort key
{"type": "sort","by": "-categoryinfo.size"},
// To visualize, use "pie" transformation to add layout_start, layout_end, and layout_mid fields to each page object
// These fields contain angles at which to start and stop drawing arcs. First element's start will be 0, and last element's end will be 360 degrees (in radians)
{"type": "pie","field": "categoryinfo.size"}
]
}
],
// Scales are like functions -- marks use them to convert a data value into a visual value, like x or y coordinate on the graph, or a color value.
"scales": [
{
// This scale will be used to assign a color to each slice, using a palette of 10 colors
"name": "color",
"domain": {"data": "table","field": "title"},
"range": "category10",
"type": "ordinal"
}
],
"marks": [
{
// This mark draws the actual pie chart from the data source
// Each element is an arc between layout_start and layout_end angles (as calculated by the pie transformation)
// drawn with a given radius, stroke, and fill.
"from": {"data": "table"},
"type": "arc",
"properties": {
"enter": {
"fill": {"scale": "color","field": "title"},
"outerRadius": {"value": 200},
"startAngle": {"field": "layout_start"},
"endAngle": {"field": "layout_end"},
"stroke": {"value": "white"},
"strokeWidth": {"value": 1}
}
}
},
{
// This mark draws labels around the pie chart after the pie chart has been drawn
"type": "text",
// Before drawing, we need to perform a number of calculations to figure out the exact location and orientation of the text
"from": {
"data": "table",
"transform": [
// For each data point (datum), each of these transformations will be ran in order.
// Formula transformation evaluates the expression and assigns result to the datapoint
// Size of the pie slice, in degrees: sliceSize = (end - start) * 180 / Pi
{ "type": "formula", "field": "sliceSize", "expr": "(datum.layout_end - datum.layout_start)*180/PI" },
// Draw text only if the slice of the arc is more than 2 degrees to avoid overcrowding
{ "type": "filter", "test": "datum.sliceSize > 2" },
// Remove namespace from the text - keeps only text after the first ':' symbol, limits to 40 chars.
{ "type": "formula", "field": "title", "expr": "substring(datum.title, 1+indexof(datum.title,':'), 40)" },
// Determine the side of the pie chart we are on - left or right.
{ "type": "formula", "field": "invert", "expr": "datum.layout_mid*180/PI < 180 ? 1 : -1" },
// If on the left, the text should be right-aligned (go from the rim inward)
{ "type": "formula", "field": "align", "expr": "datum.invert < 0 ? 'left' : 'right'" },
// At what angle should the text be drawn relative to the point on the circle
{ "type": "formula", "field": "angle", "expr": "(datum.layout_mid*180/PI)-90*datum.invert" },
// Make font smaller for smaller pie slices
{ "type": "formula", "field": "fontSize", "expr": "datum.sliceSize > 20 ? 15 : (datum.sliceSize > 10 ? 14 : 10)" },
// Make font bold for largest pie slices
{ "type": "formula", "field": "fontWeight", "expr": "datum.sliceSize > 15 ? 'bold' : 'normal'" }
]
},
"properties": {
"enter": {
// Use the fields calculated in the transformation to draw category names
"align": {"field": "align"},
"angle": {"field": "angle"},
"baseline": {"value": "middle"},
"fill": {"value": "black"},
"fontSize": {"field": "fontSize"},
"fontWeight": {"field": "fontWeight"},
"radius": {"value": 270},
"text": {"field": "title"},
"theta": {"field": "layout_mid"}
}
}
}
]
}
</graph>
<graph>
{
"version": 2,
"width": 300,
"height": 300,
"data": [
{
// Data is retrieved from the MediaWiki API. By default it uses current wiki's "Extension by category"
"name": "table",
"url": "wikiapi:///?generator=categorymembers&gcmtitle=Category:Extensions+by+category&gcmtype=subcat&action=query&gcmlimit=max&prop=categoryinfo&formatversion=2&format=json",
// We are only interested in the content of query.pages subelement.
"format": {"property": "query.pages","type": "json"},
"transform": [
// sort in descending order using category size as the sort key
{"type": "sort","by": "-categoryinfo.size"},
// To visualize, use "pie" transformation to add layout_start, layout_end, and layout_mid fields to each page object
// These fields contain angles at which to start and stop drawing arcs. First element's start will be 0, and last element's end will be 360 degrees (in radians)
{"type": "pie","field": "categoryinfo.size"}
]
}
],
// Scales are like functions -- marks use them to convert a data value into a visual value, like x or y coordinate on the graph, or a color value.
"scales": [
{
// This scale will be used to assign a color to each slice, using a palette of 10 colors
"name": "color",
"domain": {"data": "table","field": "title"},
"range": "category10",
"type": "ordinal"
}
],
"marks": [
{
// This mark draws the actual pie chart from the data source
// Each element is an arc between layout_start and layout_end angles (as calculated by the pie transformation)
// drawn with a given radius, stroke, and fill.
"from": {"data": "table"},
"type": "arc",
"properties": {
"enter": {
"fill": {"scale": "color","field": "title"},
"outerRadius": {"value": 200},
"startAngle": {"field": "layout_start"},
"endAngle": {"field": "layout_end"},
"stroke": {"value": "white"},
"strokeWidth": {"value": 1}
}
}
},
{
// This mark draws labels around the pie chart after the pie chart has been drawn
"type": "text",
// Before drawing, we need to perform a number of calculations to figure out the exact location and orientation of the text
"from": {
"data": "table",
"transform": [
// For each data point (datum), each of these transformations will be ran in order.
// Formula transformation evaluates the expression and assigns result to the datapoint
// Size of the pie slice, in degrees: sliceSize = (end - start) * 180 / Pi
{ "type": "formula", "field": "sliceSize", "expr": "(datum.layout_end - datum.layout_start)*180/PI" },
// Draw text only if the slice of the arc is more than 2 degrees to avoid overcrowding
{ "type": "filter", "test": "datum.sliceSize > 2" },
// Remove namespace from the text - keeps only text after the first ':' symbol, limits to 40 chars.
{ "type": "formula", "field": "title", "expr": "substring(datum.title, 1+indexof(datum.title,':'), 40)" },
// Determine the side of the pie chart we are on - left or right.
{ "type": "formula", "field": "invert", "expr": "datum.layout_mid*180/PI < 180 ? 1 : -1" },
// If on the left, the text should be right-aligned (go from the rim inward)
{ "type": "formula", "field": "align", "expr": "datum.invert < 0 ? 'left' : 'right'" },
// At what angle should the text be drawn relative to the point on the circle
{ "type": "formula", "field": "angle", "expr": "(datum.layout_mid*180/PI)-90*datum.invert" },
// Make font smaller for smaller pie slices
{ "type": "formula", "field": "fontSize", "expr": "datum.sliceSize > 20 ? 15 : (datum.sliceSize > 10 ? 14 : 10)" },
// Make font bold for largest pie slices
{ "type": "formula", "field": "fontWeight", "expr": "datum.sliceSize > 15 ? 'bold' : 'normal'" }
]
},
"properties": {
"enter": {
// Use the fields calculated in the transformation to draw category names
"align": {"field": "align"},
"angle": {"field": "angle"},
"baseline": {"value": "middle"},
"fill": {"value": "black"},
"fontSize": {"field": "fontSize"},
"fontWeight": {"field": "fontWeight"},
"radius": {"value": 270},
"text": {"field": "title"},
"theta": {"field": "layout_mid"}
}
}
}
]
}
</graph>
