Source: http://www.sidc.be/silso/datafiles
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Sunspots are temporary phenomena on the Sun's photosphere that appear as spots darker
than the surrounding areas. They are regions of reduced surface temperature caused by
concentrations of magnetic field flux that inhibit convection.
Sunspots usually appear in pairs of opposite magnetic polarity.
Their number varies according to the approximately 11-year solar cycle.

This is a good example for time series application.
Use only last column of data.
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Year    Sunspot number
1700	8.3
1701	18.3
1702	26.7
1703	38.3
1704	60
1705	96.7
1706	48.3
1707	33.3
1708	16.7
1709	13.3
1710	5
1711	0
1712	0
1713	3.3
1714	18.3
1715	45
1716	78.3
1717	105
1718	100
1719	65
1720	46.7
1721	43.3
1722	36.7
1723	18.3
1724	35
1725	66.7
1726	130
1727	203.3
1728	171.7
1729	121.7
1730	78.3
1731	58.3
1732	18.3
1733	8.3
1734	26.7
1735	56.7
1736	116.7
1737	135
1738	185
1739	168.3
1740	121.7
1741	66.7
1742	33.3
1743	26.7
1744	8.3
1745	18.3
1746	36.7
1747	66.7
1748	100
1749	134.8
1750	139
1751	79.5
1752	79.7
1753	51.2
1754	20.3
1755	16
1756	17
1757	54
1758	79.3
1759	90
1760	104.8
1761	143.2
1762	102
1763	75.2
1764	60.7
1765	34.8
1766	19
1767	63
1768	116.3
1769	176.8
1770	168
1771	136
1772	110.8
1773	58
1774	51
1775	11.7
1776	33
1777	154.2
1778	257.3
1779	209.8
1780	141.3
1781	113.5
1782	64.2
1783	38
1784	17
1785	40.2
1786	138.2
1787	220
1788	218.2
1789	196.8
1790	149.8
1791	111
1792	100
1793	78.2
1794	68.3
1795	35.5
1796	26.7
1797	10.7
1798	6.8
1799	11.3
1800	24.2
1801	56.7
1802	75
1803	71.8
1804	79.2
1805	70.3
1806	46.8
1807	16.8
1808	13.5
1809	4.2
1810	0
1811	2.3
1812	8.3
1813	20.3
1814	23.2
1815	59
1816	76.3
1817	68.3
1818	52.9
1819	38.5
1820	24.2
1821	9.2
1822	6.3
1823	2.2
1824	11.4
1825	28.2
1826	59.9
1827	83
1828	108.5
1829	115.2
1830	117.4
1831	80.8
1832	44.3
1833	13.4
1834	19.5
1835	85.8
1836	192.7
1837	227.3
1838	168.7
1839	143
1840	105.5
1841	63.3
1842	40.3
1843	18.1
1844	25.1
1845	65.8
1846	102.7
1847	166.3
1848	208.3
1849	182.5
1850	126.3
1851	122
1852	102.7
1853	74.1
1854	39
1855	12.7
1856	8.2
1857	43.4
1858	104.4
1859	178.3
1860	182.2
1861	146.6
1862	112.1
1863	83.5
1864	89.2
1865	57.8
1866	30.7
1867	13.9
1868	62.8
1869	123.6
1870	232
1871	185.3
1872	169.2
1873	110.1
1874	74.5
1875	28.3
1876	18.9
1877	20.7
1878	5.7
1879	10
1880	53.7
1881	90.5
1882	99
1883	106.1
1884	105.8
1885	86.3
1886	42.4
1887	21.8
1888	11.2
1889	10.4
1890	11.8
1891	59.5
1892	121.7
1893	142
1894	130
1895	106.6
1896	69.4
1897	43.8
1898	44.4
1899	20.2
1900	15.7
1901	4.6
1902	8.5
1903	40.8
1904	70.1
1905	105.5
1906	90.1
1907	102.8
1908	80.9
1909	73.2
1910	30.9
1911	9.5
1912	6
1913	2.4
1914	16.1
1915	79
1916	95
1917	173.6
1918	134.6
1919	105.7
1920	62.7
1921	43.5
1922	23.7
1923	9.7
1924	27.9
1925	74
1926	106.5
1927	114.7
1928	129.7
1929	108.2
1930	59.4
1931	35.1
1932	18.6
1933	9.2
1934	14.6
1935	60.2
1936	132.8
1937	190.6
1938	182.6
1939	148
1940	113
1941	79.2
1942	50.8
1943	27.1
1944	16.1
1945	55.3
1946	154.3
1947	214.7
1948	193
1949	190.7
1950	118.9
1951	98.3
1952	45
1953	20.1
1954	6.6
1955	54.2
1956	200.7
1957	269.3
1958	261.7
1959	225.1
1960	159
1961	76.4
1962	53.4
1963	39.9
1964	15
1965	22
1966	66.8
1967	132.9
1968	150
1969	149.4
1970	148
1971	94.4
1972	97.6
1973	54.1
1974	49.2
1975	22.5
1976	18.4
1977	39.3
1978	131
1979	220.1
1980	218.9
1981	198.9
1982	162.4
1983	91
1984	60.5
1985	20.6
1986	14.8
1987	33.9
1988	123
1989	211.1
1990	191.8
1991	203.3
1992	133
1993	76.1
1994	44.9
1995	25.1
1996	11.6
1997	28.9
1998	88.3
1999	136.3
2000	173.9
2001	170.4
2002	163.6
2003	99.3
2004	65.3
2005	45.8
2006	24.7
2007	12.6
2008	4.2
2009	4.8
2010	24.9
2011	80.8
2012	84.5
2013	94
2014	113.3
2015	69.8
2016	39.8
2017	21.7
2018	7
2019	3.6
2020	8.8