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libhxl-js

JavaScript support library for the Humanitarian Exchange Language (HXL) data standard.

http://hxlstandard.org

Overview

This library supports high-level filtering and aggregation operations on HXL datasets. Auto-generated API documentation (which may or may not be up to date) is available at https://hxlstandard.github.io/libhxl-js/

Usage

Load a CSV dataset from the web:

Requires that the Papa Parse CSV library be loaded before HXL (there is a copy bundled in lib/, with permission):

hxl.load('http://example.org/dataset.csv', function (dataset) {
    console.log('Dataset has ' + dataset.columns.length + ' columns.');
});

The HXL library will soon also support autodetecting the availability of D3 and JQuery-based CSV parsing.

Create a dataset from array data

var rawData = [
    [ "Organisation", "Cluster", "Province" ],
    [ "#org", "#sector", "#adm1" ],
    [ "Org A", "WASH", "Coastal Province" ],
    [ "Org B", "Health", "Mountain Province" ],
    [ "Org C", "Education", "Coastal Province" ],
    [ "Org A", "WASH", "Plains Province" ],
];

var dataset = hxl.wrap(rawData);
console.log('Dataset has ' + dataset.columns.length + ' columns');

Read a remote JSON-encoded HXL dataset

fetch("http://example.org/data/sample.hxl.json").then(r => {
    r.json().then(rawData => {
        let dataset = hxl.wrap(rawData);
        console.log('Dataset has ' + dataset.columns.length + ' columns');
    });
});

Classes

hxl.classes.Source

Note: Any method that takes a hxl.classes.TagPattern as an argument can accept a string representation instead (e.g. "#affected+f-adults"). Any method that takes a list of TagPatterns as an argument can accept a single pattern (as above) or list of patterns.

Properties

Property Data type Description
columns array of hxl.classes.Column All the column objects for the dataset
rows array of hxl.classes.Row All the row objects for the dataset (excluding header and hashtag row)
rawData array of arrays Get all the raw row data for the dataset (excluding header and hashtag row)
headers array of strings Get all the text headers as strings
tags array of strings Get all the hashtags (without attributes) as strings
displayTags array of strings Get all the hasthag specs (with attributes) as strings

Row iteration methods

Method | Description -- | -- | -- each(callback) | iterator through each row of the dataset, invoking callback with the row, dataset, and row number as arguments forEach(callback) | synonym for each() iterator() | return a simple iterator with a next() function (but not done(); it returns null when finished)

Aggregate methods

Use these methods to extract aggregate values from the dataset.

Method Result Description
getSum(tagPattern) number Sum of all numeric values in the first column matching tagPattern
getMin(tagPattern) number Lowest of all numeric values in the first column matching tagPattern
getMax(tagPattern) number Highest of all numeric values in the first column matching tagPattern
getValues(tagPattern) array List of unique values in the first column matching tagPattern
getRawValues(tagPattern) array List of all values in the first column matching tagPattern (including repetitions and nulls), in the original order

Filter methods

The return value from a filter is always a new (virtual) dataset with the filter applied.

Method Description
withRows(predicates) Include only rows matching (any of) predicates
withoutRows(predicates) Include only rows not matching (any of) predicates
withColumns(tagPatterns) Include only columns matching (any of) tagPatterns
withoutColumns(tagPatterns) Include only columns not matching (any of) tagPatterns
count(tagPatterns, aggregate=null) Aggregate data (like in a pivot table) for the columns matching tagPatterns, and optionally produce aggregate values for the first column matching the tag pattern aggregate
rename(tagPattern, spec, header=null, index=0) Rename the index column matching tagPattern to use the hashtag and attributes spec and optionally the new header header
sort(tagPatterns, reverse=false) Sort the dataset using columns matching tagPatterns as keys, with numeric comparison where possible
preview(maxRows=10) Filter to a maximum of maxRows rows.
catch() Create a permanent copy of the data at this point in the pipeline, so that earlier filters don't have to be rerun.
index() Number repeated tag specs by adding the attributes +i0, +i1, etc to simplify processing.

Other methods

Method Result Description
isNumbery(tagPattern) boolean Return true if the first column matching tagPattern contains mainly numbers
iterator() object Return a simple iterator with a next() method for reading through the rows (returns null at the end)
exportArray() array of arrays Export the whole dataset as an array of arrays (including the headers and hashtag row)
hasColumn(tagPattern) boolean true if the dataset has at least one column matching tagPattern
getMatchingColumns(tagPattern) array of int List of 0-based indices for columns matching tagPattern

Filter examples

Filters create a new virtual version of the dataset, on the fly. The original dataset is unmodified.

Column filtering

Include only specific columns

dataset.withColumns(['#org', '#sector', '#adm1']).each(...);

Remove specific columns

dataset.withoutColumns('#contact+email').each(...);

Row filtering

Include only specific rows

dataset.withRows('#sector=WASH').each(...);

Remove specific rows

dataset.withoutRows('#status=Unreleased').each(...);

Test an entire row

dataset.withRows(function (row) { 
    return row.get('#population+targeted+num') < row.get('#population+affected+num');
}).each(...);

Aggregation

Count values of #adm1

dataset.count('#adm1').each(...);

Count combinations of #adm1 and #sector

dataset.count(['#adm1', '#sector']).each(...);

Chain filters together

Count #adm only in the WASH sector:

dataset.withRows('#sector=WASH').count('#adm1').each(row => {
    // do something with each row
});

or

var iterator = dataset.iterator();
var row = iterator.next();
while (row != null) {
    // do something with each row
    row = iterator.next();
}

Tests

To run the unit tests, open the file tests/index.html in a modern web browser. You may need to install them in a web server to avoid cross-domain errors in browsers with strict security models.

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JavaScript support library for the Humanitarian Exchange Language (HXL) data standard.

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