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<FONT color="green">157</FONT> Number value = (Number) values.get(0);<a name="line.157"></a><FONT color="green">158</FONT> result = value.doubleValue();<a name="line.158"></a><FONT color="green">159</FONT> }<a name="line.159"></a><FONT color="green">160</FONT> }<a name="line.160"></a><FONT color="green">161</FONT> else {<a name="line.161"></a><FONT color="green">162</FONT> Number value1 = (Number) values.get(count / 2 - 1);<a name="line.162"></a><FONT color="green">163</FONT> Number value2 = (Number) values.get(count / 2);<a name="line.163"></a><FONT color="green">164</FONT> result = (value1.doubleValue() + value2.doubleValue()) <a name="line.164"></a><FONT color="green">165</FONT> / 2.0;<a name="line.165"></a><FONT color="green">166</FONT> }<a name="line.166"></a><FONT color="green">167</FONT> }<a name="line.167"></a><FONT color="green">168</FONT> }<a name="line.168"></a><FONT color="green">169</FONT> return result;<a name="line.169"></a><FONT color="green">170</FONT> }<a name="line.170"></a><FONT color="green">171</FONT> <a name="line.171"></a><FONT color="green">172</FONT> /**<a name="line.172"></a><FONT color="green">173</FONT> * Calculates the median for a sublist within a list of values <a name="line.173"></a><FONT color="green">174</FONT> * (<code>Number</code> objects).<a name="line.174"></a><FONT color="green">175</FONT> * <a name="line.175"></a><FONT color="green">176</FONT> * @param values the values (in any order).<a name="line.176"></a><FONT color="green">177</FONT> * @param start the start index.<a name="line.177"></a><FONT color="green">178</FONT> * @param end the end index.<a name="line.178"></a><FONT color="green">179</FONT> * <a name="line.179"></a><FONT color="green">180</FONT> * @return The median.<a name="line.180"></a><FONT color="green">181</FONT> */<a name="line.181"></a><FONT color="green">182</FONT> public static double calculateMedian(List values, int start, int end) {<a name="line.182"></a><FONT color="green">183</FONT> return calculateMedian(values, start, end, true);<a name="line.183"></a><FONT color="green">184</FONT> }<a name="line.184"></a><FONT color="green">185</FONT> <a name="line.185"></a><FONT color="green">186</FONT> /**<a name="line.186"></a><FONT color="green">187</FONT> * Calculates the median for a sublist within a list of values <a name="line.187"></a><FONT color="green">188</FONT> * (<code>Number</code> objects). The entire list will be sorted if the <a name="line.188"></a><FONT color="green">189</FONT> * <code>ascending</code< argument is <code>false</code>.<a name="line.189"></a><FONT color="green">190</FONT> * <a name="line.190"></a><FONT color="green">191</FONT> * @param values the values.<a name="line.191"></a><FONT color="green">192</FONT> * @param start the start index.<a name="line.192"></a><FONT color="green">193</FONT> * @param end the end index.<a name="line.193"></a><FONT color="green">194</FONT> * @param copyAndSort a flag that that controls whether the list of values <a name="line.194"></a><FONT color="green">195</FONT> * is copied and sorted.<a name="line.195"></a><FONT color="green">196</FONT> * <a name="line.196"></a><FONT color="green">197</FONT> * @return The median.<a name="line.197"></a><FONT color="green">198</FONT> */<a name="line.198"></a><FONT color="green">199</FONT> public static double calculateMedian(List values, int start, int end,<a name="line.199"></a><FONT color="green">200</FONT> boolean copyAndSort) {<a name="line.200"></a><FONT color="green">201</FONT> <a name="line.201"></a><FONT color="green">202</FONT> double result = Double.NaN;<a name="line.202"></a><FONT color="green">203</FONT> if (copyAndSort) {<a name="line.203"></a><FONT color="green">204</FONT> List working = new ArrayList(end - start + 1);<a name="line.204"></a><FONT color="green">205</FONT> for (int i = start; i <= end; i++) {<a name="line.205"></a><FONT color="green">206</FONT> working.add(values.get(i)); <a name="line.206"></a><FONT color="green">207</FONT> }<a name="line.207"></a><FONT color="green">208</FONT> Collections.sort(working); <a name="line.208"></a><FONT color="green">209</FONT> result = calculateMedian(working, false);<a name="line.209"></a><FONT color="green">210</FONT> }<a name="line.210"></a><FONT color="green">211</FONT> else {<a name="line.211"></a><FONT color="green">212</FONT> int count = end - start + 1;<a name="line.212"></a><FONT color="green">213</FONT> if (count > 0) {<a name="line.213"></a><FONT color="green">214</FONT> if (count % 2 == 1) {<a name="line.214"></a><FONT color="green">215</FONT> if (count > 1) {<a name="line.215"></a><FONT color="green">216</FONT> Number value <a name="line.216"></a><FONT color="green">217</FONT> = (Number) values.get(start + (count - 1) / 2);<a name="line.217"></a><FONT color="green">218</FONT> result = value.doubleValue();<a name="line.218"></a><FONT color="green">219</FONT> }<a name="line.219"></a><FONT color="green">220</FONT> else {<a name="line.220"></a><FONT color="green">221</FONT> Number value = (Number) values.get(start);<a name="line.221"></a><FONT color="green">222</FONT> result = value.doubleValue();<a name="line.222"></a><FONT color="green">223</FONT> }<a name="line.223"></a><FONT color="green">224</FONT> }<a name="line.224"></a><FONT color="green">225</FONT> else {<a name="line.225"></a><FONT color="green">226</FONT> Number value1 = (Number) values.get(start + count / 2 - 1);<a name="line.226"></a><FONT color="green">227</FONT> Number value2 = (Number) values.get(start + count / 2);<a name="line.227"></a><FONT color="green">228</FONT> result <a name="line.228"></a><FONT color="green">229</FONT> = (value1.doubleValue() + value2.doubleValue()) / 2.0;<a name="line.229"></a><FONT color="green">230</FONT> }<a name="line.230"></a><FONT color="green">231</FONT> }<a name="line.231"></a><FONT color="green">232</FONT> }<a name="line.232"></a><FONT color="green">233</FONT> return result; <a name="line.233"></a><FONT color="green">234</FONT> <a name="line.234"></a><FONT color="green">235</FONT> }<a name="line.235"></a><FONT color="green">236</FONT> <a name="line.236"></a><FONT color="green">237</FONT> /**<a name="line.237"></a><FONT color="green">238</FONT> * Returns the standard deviation of a set of numbers.<a name="line.238"></a><FONT color="green">239</FONT> *<a name="line.239"></a><FONT color="green">240</FONT> * @param data the data.<a name="line.240"></a><FONT color="green">241</FONT> *<a name="line.241"></a><FONT color="green">242</FONT> * @return The standard deviation of a set of numbers.<a name="line.242"></a><FONT color="green">243</FONT> */<a name="line.243"></a><FONT color="green">244</FONT> public static double getStdDev(Number[] data) {<a name="line.244"></a><FONT color="green">245</FONT> double avg = calculateMean(data);<a name="line.245"></a><FONT color="green">246</FONT> double sum = 0.0;<a name="line.246"></a><FONT color="green">247</FONT> <a name="line.247"></a><FONT color="green">248</FONT> for (int counter = 0; counter < data.length; counter++) {<a name="line.248"></a><FONT color="green">249</FONT> double diff = data[counter].doubleValue() - avg;<a name="line.249"></a><FONT color="green">250</FONT> sum = sum + diff * diff;<a name="line.250"></a><FONT color="green">251</FONT> }<a name="line.251"></a><FONT color="green">252</FONT> return Math.sqrt(sum / (data.length - 1));<a name="line.252"></a><FONT color="green">253</FONT> }<a name="line.253"></a><FONT color="green">254</FONT> <a name="line.254"></a><FONT color="green">255</FONT> /**<a name="line.255"></a><FONT color="green">256</FONT> * Fits a straight line to a set of (x, y) data, returning the slope and<a name="line.256"></a><FONT color="green">257</FONT> * intercept.<a name="line.257"></a><FONT color="green">258</FONT> *<a name="line.258"></a><FONT color="green">259</FONT> * @param xData the x-data.<a name="line.259"></a><FONT color="green">260</FONT> * @param yData the y-data.<a name="line.260"></a><FONT color="green">261</FONT> *<a name="line.261"></a><FONT color="green">262</FONT> * @return A double array with the intercept in [0] and the slope in [1].<a name="line.262"></a><FONT color="green">263</FONT> */<a name="line.263"></a><FONT color="green">264</FONT> public static double[] getLinearFit(Number[] xData, Number[] yData) {<a name="line.264"></a><FONT color="green">265</FONT> <a name="line.265"></a><FONT color="green">266</FONT> // check arguments...<a name="line.266"></a><FONT color="green">267</FONT> if (xData.length != yData.length) {<a name="line.267"></a><FONT color="green">268</FONT> throw new IllegalArgumentException(<a name="line.268"></a><FONT color="green">269</FONT> "Statistics.getLinearFit(): array lengths must be equal.");<a name="line.269"></a><FONT color="green">270</FONT> }<a name="line.270"></a><FONT color="green">271</FONT> <a name="line.271"></a><FONT color="green">272</FONT> double[] result = new double[2];<a name="line.272"></a><FONT color="green">273</FONT> // slope<a name="line.273"></a><FONT color="green">274</FONT> result[1] = getSlope(xData, yData);<a name="line.274"></a><FONT color="green">275</FONT> // intercept<a name="line.275"></a><FONT color="green">276</FONT> result[0] = calculateMean(yData) - result[1] * calculateMean(xData);<a name="line.276"></a><FONT color="green">277</FONT> <a name="line.277"></a><FONT color="green">278</FONT> return result;<a name="line.278"></a><FONT color="green">279</FONT> <a name="line.279"></a><FONT color="green">280</FONT> }<a name="line.280"></a><FONT color="green">281</FONT> <a name="line.281"></a><FONT color="green">282</FONT> /**<a name="line.282"></a><FONT color="green">283</FONT> * Finds the slope of a regression line using least squares.<a name="line.283"></a><FONT color="green">284</FONT> *<a name="line.284"></a><FONT color="green">285</FONT> * @param xData an array of Numbers (the x values).<a name="line.285"></a><FONT color="green">286</FONT> * @param yData an array of Numbers (the y values).<a name="line.286"></a><FONT color="green">287</FONT> *<a name="line.287"></a><FONT color="green">288</FONT> * @return The slope.<a name="line.288"></a><FONT color="green">289</FONT> */<a name="line.289"></a><FONT color="green">290</FONT> public static double getSlope(Number[] xData, Number[] yData) {<a name="line.290"></a><FONT color="green">291</FONT> <a name="line.291"></a><FONT color="green">292</FONT> // check arguments...<a name="line.292"></a><FONT color="green">293</FONT> if (xData.length != yData.length) {<a name="line.293"></a><FONT color="green">294</FONT> throw new IllegalArgumentException("Array lengths must be equal.");<a name="line.294"></a><FONT color="green">295</FONT> }<a name="line.295"></a><FONT color="green">296</FONT> <a name="line.296"></a><FONT color="green">297</FONT> // ********* stat function for linear slope ********<a name="line.297"></a><FONT color="green">298</FONT> // y = a + bx<a name="line.298"></a><FONT color="green">299</FONT> // a = ybar - b * xbar<a name="line.299"></a><FONT color="green">300</FONT> // sum(x * y) - (sum (x) * sum(y)) / n<a name="line.300"></a><FONT color="green">301</FONT> // b = ------------------------------------<a name="line.301"></a><FONT color="green">302</FONT> // sum (x^2) - (sum(x)^2 / n<a name="line.302"></a><FONT color="green">303</FONT> // *************************************************<a name="line.303"></a><FONT color="green">304</FONT> <a name="line.304"></a><FONT color="green">305</FONT> // sum of x, x^2, x * y, y<a name="line.305"></a><FONT color="green">306</FONT> double sx = 0.0, sxx = 0.0, sxy = 0.0, sy = 0.0;<a name="line.306"></a><FONT color="green">307</FONT> int counter;<a name="line.307"></a><FONT color="green">308</FONT> for (counter = 0; counter < xData.length; counter++) {<a name="line.308"></a><FONT color="green">309</FONT> sx = sx + xData[counter].doubleValue();<a name="line.309"></a><FONT color="green">310</FONT> sxx = sxx + Math.pow(xData[counter].doubleValue(), 2);<a name="line.310"></a><FONT color="green">311</FONT> sxy = sxy + yData[counter].doubleValue() <a name="line.311"></a><FONT color="green">312</FONT> * xData[counter].doubleValue();<a name="line.312"></a><FONT color="green">313</FONT> sy = sy + yData[counter].doubleValue();<a name="line.313"></a><FONT color="green">314</FONT> }<a name="line.314"></a><FONT color="green">315</FONT> return (sxy - (sx * sy) / counter) / (sxx - (sx * sx) / counter);<a name="line.315"></a>⌨️ 快捷键说明
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