30:T443,md`### Geo With reference from http://www.movable-type.co.uk/scripts/latlong.html #### d2r ~~~js /** * Converts degrees to radians * @param {number} d * @returns {number} */ ~~~ #### r2d ~~~js /** * Converts radians to degrees * @param {number} r * @returns {number} */ ~~~ #### m2m ~~~js /** * Converts meters to miles * @param {number} m * @returns {number} */ ~~~ #### a ~~~js /** * Angle in radians between two points on the Earth * @param {Latitude} lat1 * @param {Longitude} lon1 * @param {Latitude} lat2 * @param {Longitude} lon2 * @returns {number} angle in radians */ ~~~ #### bearingR ~~~js /** * Bearing in radians from point 1 to point 2 on Earth * @param {Latitude} lat1 * @param {Longitude} lon1 * @param {Latitude} lat2 * @param {Longitude} lon2 * @returns {number} angle in radians */ ~~~ #### bearing ~~~js /** * Converts bearing from radians to degrees * @param {number} bR * @returns {number} */ ~~~ #### distance ~~~js /** * Finds distance in miles represented by angle between two points * @param {number} a * @returns {number} */ ~~~ `31:[] 2e:{"title":"Utility Library","cells":[{"id":0,"value":"md`# Utility Library`","pinned":false,"hidden":false,"mode":"ojs"},{"id":4,"value":"md`JavaScript utility functions for Observable work. Originally a [Gist](https://gist.github.com/anbnyc/874f07fbe26d9bbf8fd67be2e8a8682c). Unit tests [here](https://observablehq.com/@anbnyc/utility-library-spec).\n\n## D3 utilities\n#### createMerge\n**Note**: this function is made mostly obsolete by D3v5's \\`.join\\` method.\n~~~js\n/**\n * Binds elements to data and merges with existing D3 selection\n * @param {D3 selection} parent\n * @param {string} el\n * @param {string} cl\n * @param {Array} data\n * @param {function} acc\n * @return {D3 selection}\n */\n~~~`","pinned":false,"hidden":false,"mode":"ojs"},{"id":10,"value":"function createMerge(parent, el, cl, data, acc){\n\treturn parent.selectAll(el+ (cl ? cl.split(' ').map(c => '.'+c).join('') : ''))\n\t\t.data(data, acc & ((d,i) => acc(d,i)))\n .join(el)\n .attr('class', cl)\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":18,"value":"md`#### createOnce\n~~~js\n/**\n * Binds elements to null data to create once\n * @param {D3 selection} parent\n * @param {string} el\n * @param {string} cl\n * @return {D3 selection}\n */\n~~~`","pinned":false,"hidden":false,"mode":"ojs"},{"id":11,"value":"function createOnce(parent, el, cl) { \n return createMerge(parent, el, cl, [null])\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":92,"value":"md`## Observable utilities\n#### makeHtmlDropdown\n~~~js\n/**\n * Generates an HTML string for a custom dropdown menu\n * @param {Array} options\n * @param {string} [name]\n * @param {string} [selected]\n * @returns {string}\n */\n~~~`","pinned":false,"hidden":false,"mode":"ojs"},{"id":95,"value":"makeHtmlDropdown = (options, name, selected) => \n `