median.json

{
    "id": "median",
    "summary": "Statistical median",
    "description": "The statistical median of an array of numbers is the value separating the higher half from the lower half of the data.\n\nAn array without non-`null` elements resolves always with `null`.\n\n**Remarks:**\n\n* For symmetric arrays, the result is equal to the ``mean()``.\n* The median can also be calculated by computing the ``quantiles()`` with a probability of *0.5*.",
    "categories": [
        "math > statistics",
        "reducer"
    ],
    "parameters": [
        {
            "name": "data",
            "description": "An array of numbers.",
            "schema": {
                "type": "array",
                "items": {
                    "type": [
                        "number",
                        "null"
                    ]
                }
            }
        },
        {
            "name": "ignore_nodata",
            "description": "Indicates whether no-data values are ignored or not. Ignores them by default. Setting this flag to `false` considers no-data values so that `null` is returned if any value is such a value.",
            "schema": {
                "type": "boolean"
            },
            "default": true,
            "optional": true
        }
    ],
    "returns": {
        "description": "The computed statistical median.",
        "schema": {
            "type": [
                "number",
                "null"
            ]
        }
    },
    "examples": [
        {
            "arguments": {
                "data": [
                    1,
                    3,
                    3,
                    6,
                    7,
                    8,
                    9
                ]
            },
            "returns": 6
        },
        {
            "arguments": {
                "data": [
                    1,
                    2,
                    3,
                    4,
                    5,
                    6,
                    8,
                    9
                ]
            },
            "returns": 4.5
        },
        {
            "arguments": {
                "data": [
                    -1,
                    -0.5,
                    null,
                    1
                ]
            },
            "returns": -0.5
        },
        {
            "arguments": {
                "data": [
                    -1,
                    0,
                    null,
                    1
                ],
                "ignore_nodata": false
            },
            "returns": null
        },
        {
            "description": "The input array is empty: return `null`.",
            "arguments": {
                "data": []
            },
            "returns": null
        },
        {
            "description": "The input array has only `null` elements: return `null`.",
            "arguments": {
                "data": [
                    null,
                    null
                ]
            },
            "returns": null
        }
    ],
    "links": [
        {
            "rel": "about",
            "href": "http://mathworld.wolfram.com/StatisticalMedian.html",
            "title": "Statistical Median explained by Wolfram MathWorld"
        }
    ],
    "process_graph": {
        "quantiles": {
            "process_id": "quantiles",
            "arguments": {
                "data": {
                    "from_parameter": "data"
                },
                "probabilities": [
                    0.5
                ],
                "ignore_nodata": {
                    "from_parameter": "ignore_nodata"
                }
            }
        },
        "array_element": {
            "process_id": "array_element",
            "arguments": {
                "data": {
                    "from_node": "quantiles"
                },
                "return_nodata": true,
                "index": 0
            },
            "result": true
        }
    }
}