regression.html

jfreechart1。0。2的api。

<FONT color="green">146</FONT>         *<a name="line.146"></a>
<FONT color="green">147</FONT>         * @param data  the data.<a name="line.147"></a>
<FONT color="green">148</FONT>         *<a name="line.148"></a>
<FONT color="green">149</FONT>         * @return The parameters.<a name="line.149"></a>
<FONT color="green">150</FONT>         */<a name="line.150"></a>
<FONT color="green">151</FONT>        public static double[] getPowerRegression(double[][] data) {<a name="line.151"></a>
<FONT color="green">152</FONT>    <a name="line.152"></a>
<FONT color="green">153</FONT>            int n = data.length;<a name="line.153"></a>
<FONT color="green">154</FONT>            if (n &lt; 2) {<a name="line.154"></a>
<FONT color="green">155</FONT>                throw new IllegalArgumentException("Not enough data.");<a name="line.155"></a>
<FONT color="green">156</FONT>            }<a name="line.156"></a>
<FONT color="green">157</FONT>    <a name="line.157"></a>
<FONT color="green">158</FONT>            double sumX = 0;<a name="line.158"></a>
<FONT color="green">159</FONT>            double sumY = 0;<a name="line.159"></a>
<FONT color="green">160</FONT>            double sumXX = 0;<a name="line.160"></a>
<FONT color="green">161</FONT>            double sumXY = 0;<a name="line.161"></a>
<FONT color="green">162</FONT>            for (int i = 0; i &lt; n; i++) {<a name="line.162"></a>
<FONT color="green">163</FONT>                double x = Math.log(data[i][0]);<a name="line.163"></a>
<FONT color="green">164</FONT>                double y = Math.log(data[i][1]);<a name="line.164"></a>
<FONT color="green">165</FONT>                sumX += x;<a name="line.165"></a>
<FONT color="green">166</FONT>                sumY += y;<a name="line.166"></a>
<FONT color="green">167</FONT>                double xx = x * x;<a name="line.167"></a>
<FONT color="green">168</FONT>                sumXX += xx;<a name="line.168"></a>
<FONT color="green">169</FONT>                double xy = x * y;<a name="line.169"></a>
<FONT color="green">170</FONT>                sumXY += xy;<a name="line.170"></a>
<FONT color="green">171</FONT>            }<a name="line.171"></a>
<FONT color="green">172</FONT>            double sxx = sumXX - (sumX * sumX) / n;<a name="line.172"></a>
<FONT color="green">173</FONT>            double sxy = sumXY - (sumX * sumY) / n;<a name="line.173"></a>
<FONT color="green">174</FONT>            double xbar = sumX / n;<a name="line.174"></a>
<FONT color="green">175</FONT>            double ybar = sumY / n;<a name="line.175"></a>
<FONT color="green">176</FONT>    <a name="line.176"></a>
<FONT color="green">177</FONT>            double[] result = new double[2];<a name="line.177"></a>
<FONT color="green">178</FONT>            result[1] = sxy / sxx;<a name="line.178"></a>
<FONT color="green">179</FONT>            result[0] = Math.pow(Math.exp(1.0), ybar - result[1] * xbar);<a name="line.179"></a>
<FONT color="green">180</FONT>    <a name="line.180"></a>
<FONT color="green">181</FONT>            return result;<a name="line.181"></a>
<FONT color="green">182</FONT>    <a name="line.182"></a>
<FONT color="green">183</FONT>        }<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>         * Returns the parameters 'a' and 'b' for an equation y = ax^b, fitted to <a name="line.186"></a>
<FONT color="green">187</FONT>         * the data using a power regression equation.  The result is returned as <a name="line.187"></a>
<FONT color="green">188</FONT>         * an array, where double[0] --&gt; a, and double[1] --&gt; b.<a name="line.188"></a>
<FONT color="green">189</FONT>         *<a name="line.189"></a>
<FONT color="green">190</FONT>         * @param data  the data.<a name="line.190"></a>
<FONT color="green">191</FONT>         * @param series  the series to fit the regression line against.<a name="line.191"></a>
<FONT color="green">192</FONT>         *<a name="line.192"></a>
<FONT color="green">193</FONT>         * @return The parameters.<a name="line.193"></a>
<FONT color="green">194</FONT>         */<a name="line.194"></a>
<FONT color="green">195</FONT>        public static double[] getPowerRegression(XYDataset data, int series) {<a name="line.195"></a>
<FONT color="green">196</FONT>    <a name="line.196"></a>
<FONT color="green">197</FONT>            int n = data.getItemCount(series);<a name="line.197"></a>
<FONT color="green">198</FONT>            if (n &lt; 2) {<a name="line.198"></a>
<FONT color="green">199</FONT>                throw new IllegalArgumentException("Not enough data.");<a name="line.199"></a>
<FONT color="green">200</FONT>            }<a name="line.200"></a>
<FONT color="green">201</FONT>    <a name="line.201"></a>
<FONT color="green">202</FONT>            double sumX = 0;<a name="line.202"></a>
<FONT color="green">203</FONT>            double sumY = 0;<a name="line.203"></a>
<FONT color="green">204</FONT>            double sumXX = 0;<a name="line.204"></a>
<FONT color="green">205</FONT>            double sumXY = 0;<a name="line.205"></a>
<FONT color="green">206</FONT>            for (int i = 0; i &lt; n; i++) {<a name="line.206"></a>
<FONT color="green">207</FONT>                double x = Math.log(data.getXValue(series, i));<a name="line.207"></a>
<FONT color="green">208</FONT>                double y = Math.log(data.getYValue(series, i));<a name="line.208"></a>
<FONT color="green">209</FONT>                sumX += x;<a name="line.209"></a>
<FONT color="green">210</FONT>                sumY += y;<a name="line.210"></a>
<FONT color="green">211</FONT>                double xx = x * x;<a name="line.211"></a>
<FONT color="green">212</FONT>                sumXX += xx;<a name="line.212"></a>
<FONT color="green">213</FONT>                double xy = x * y;<a name="line.213"></a>
<FONT color="green">214</FONT>                sumXY += xy;<a name="line.214"></a>
<FONT color="green">215</FONT>            }<a name="line.215"></a>
<FONT color="green">216</FONT>            double sxx = sumXX - (sumX * sumX) / n;<a name="line.216"></a>
<FONT color="green">217</FONT>            double sxy = sumXY - (sumX * sumY) / n;<a name="line.217"></a>
<FONT color="green">218</FONT>            double xbar = sumX / n;<a name="line.218"></a>
<FONT color="green">219</FONT>            double ybar = sumY / n;<a name="line.219"></a>
<FONT color="green">220</FONT>    <a name="line.220"></a>
<FONT color="green">221</FONT>            double[] result = new double[2];<a name="line.221"></a>
<FONT color="green">222</FONT>            result[1] = sxy / sxx;<a name="line.222"></a>
<FONT color="green">223</FONT>            result[0] = Math.pow(Math.exp(1.0), ybar - result[1] * xbar);<a name="line.223"></a>
<FONT color="green">224</FONT>    <a name="line.224"></a>
<FONT color="green">225</FONT>            return result;<a name="line.225"></a>
<FONT color="green">226</FONT>    <a name="line.226"></a>
<FONT color="green">227</FONT>        }<a name="line.227"></a>
<FONT color="green">228</FONT>    <a name="line.228"></a>
<FONT color="green">229</FONT>    }<a name="line.229"></a>




























































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