data and data1 are two strings with rainfall records of a few cities for months from January to December. The records of towns are separated by \n. The name of each town is followed by :.

const data = 
     "Rome:Jan 81.2,Feb 63.2,Mar 70.3,Apr 55.7,May 53.0,Jun 36.4,Jul 17.5,Aug 27.5,Sep 60.9,Oct 117.7,Nov 111.0,Dec 97.9" + "\n" +
     "London:Jan 48.0,Feb 38.9,Mar 39.9,Apr 42.2,May 47.3,Jun 52.1,Jul 59.5,Aug 57.2,Sep 55.4,Oct 62.0,Nov 59.0,Dec 52.9" + "\n" +
     "Paris:Jan 182.3,Feb 120.6,Mar 158.1,Apr 204.9,May 323.1,Jun 300.5,Jul 236.8,Aug 192.9,Sep 66.3,Oct 63.3,Nov 83.2,Dec 154.7" + "\n" +
     "NY:Jan 108.7,Feb 101.8,Mar 131.9,Apr 93.5,May 98.8,Jun 93.6,Jul 102.2,Aug 131.8,Sep 92.0,Oct 82.3,Nov 107.8,Dec 94.2" + "\n" +
     "Vancouver:Jan 145.7,Feb 121.4,Mar 102.3,Apr 69.2,May 55.8,Jun 47.1,Jul 31.3,Aug 37.0,Sep 59.6,Oct 116.3,Nov 154.6,Dec 171.5" + "\n" +
     "Sydney:Jan 103.4,Feb 111.0,Mar 131.3,Apr 129.7,May 123.0,Jun 129.2,Jul 102.8,Aug 80.3,Sep 69.3,Oct 82.6,Nov 81.4,Dec 78.2" + "\n" +
     "Bangkok:Jan 10.6,Feb 28.2,Mar 30.7,Apr 71.8,May 189.4,Jun 151.7,Jul 158.2,Aug 187.0,Sep 319.9,Oct 230.8,Nov 57.3,Dec 9.4" + "\n" +
     "Tokyo:Jan 49.9,Feb 71.5,Mar 106.4,Apr 129.2,May 144.0,Jun 176.0,Jul 135.6,Aug 148.5,Sep 216.4,Oct 194.1,Nov 95.6,Dec 54.4" + "\n" +
     "Beijing:Jan 3.9,Feb 4.7,Mar 8.2,Apr 18.4,May 33.0,Jun 78.1,Jul 224.3,Aug 170.0,Sep 58.4,Oct 18.0,Nov 9.3,Dec 2.7" + "\n" +
     "Lima:Jan 1.2,Feb 0.9,Mar 0.7,Apr 0.4,May 0.6,Jun 1.8,Jul 4.4,Aug 3.1,Sep 3.3,Oct 1.7,Nov 0.5,Dec 0.7";

const data1 =
     "Rome:Jan 90.2,Feb 73.2,Mar 80.3,Apr 55.7,May 53.0,Jun 36.4,Jul 17.5,Aug 27.5,Sep 60.9,Oct 147.7,Nov 121.0,Dec 97.9" + "\n" +
     "London:Jan 58.0,Feb 38.9,Mar 49.9,Apr 42.2,May 67.3,Jun 52.1,Jul 59.5,Aug 77.2,Sep 55.4,Oct 62.0,Nov 69.0,Dec 52.9" + "\n" +
     "Paris:Jan 182.3,Feb 120.6,Mar 188.1,Apr 204.9,May 323.1,Jun 350.5,Jul 336.8,Aug 192.9,Sep 66.3,Oct 63.3,Nov 83.2,Dec 154.7" + "\n" +
     "NY:Jan 128.7,Feb 121.8,Mar 151.9,Apr 93.5,May 98.8,Jun 93.6,Jul 142.2,Aug 131.8,Sep 92.0,Oct 82.3,Nov 107.8,Dec 94.2" + "\n" +
     "Vancouver:Jan 155.7,Feb 121.4,Mar 132.3,Apr 69.2,May 85.8,Jun 47.1,Jul 31.3,Aug 37.0,Sep 69.6,Oct 116.3,Nov 154.6,Dec 171.5" + "\n" +
     "Sydney:Jan 123.4,Feb 111.0,Mar 151.3,Apr 129.7,May 123.0,Jun 159.2,Jul 102.8,Aug 90.3,Sep 69.3,Oct 82.6,Nov 81.4,Dec 78.2" + "\n" +
     "Bangkok:Jan 20.6,Feb 28.2,Mar 40.7,Apr 81.8,May 189.4,Jun 151.7,Jul 198.2,Aug 197.0,Sep 319.9,Oct 230.8,Nov 57.3,Dec 9.4" + "\n" +
     "Tokyo:Jan 59.9,Feb 81.5,Mar 106.4,Apr 139.2,May 144.0,Jun 186.0,Jul 155.6,Aug 148.5,Sep 216.4,Oct 194.1,Nov 95.6,Dec 54.4" + "\n" +
     "Beijing:Jan 13.9,Feb 14.7,Mar 18.2,Apr 18.4,May 43.0,Jun 88.1,Jul 224.3,Aug 170.0,Sep 58.4,Oct 38.0,Nov 19.3,Dec 2.7" + "\n" +
     "Lima:Jan 11.2,Feb 10.9,Mar 10.7,Apr 10.4,May 10.6,Jun 11.8,Jul 14.4,Aug 13.1,Sep 23.3,Oct 1.7,Nov 0.5,Dec 10.7";

const towns = ["Rome", "London", "Paris", "NY", "Vancouver", "Sydney", "Bangkok", "Tokyo",
               "Beijing", "Lima", "Montevideo", "Caracas", "Madrid", "Berlin"]

function: mean(town, string) should return the average of rainfall for the city town and the string data or data1.

function: variance(town, string) should return the variance of rainfall for the city town and the string data or data1.

If functions mean or variance have as parameter town a city which has no records, return -1.

A reference to help: http://www.mathsisfun.com/data/standard-deviation.html
data and data1 (can be named d0 and d1 depending on the language) are adapted from: http://www.worldclimate.com

Examples

mean("London", data) => 51.19(9999999999996)
variance("London", data) => 57.42(833333333374)

Tests

mean(Rome, data1);
mean(Beijing, data);

variance(Beijing, data1);
variance(Lima, data);

Good luck!

This challenge comes from g964 on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

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Daily Challenge #216 - Rainfall

Examples

Tests