均值，中位数，模式，范围 – Java

是否有一个包含getMean() ， getMedian() ， getMode()和getRange()方法的数学库？

Answer 1

我猜你的意思是数学意思，等等。我不确定，但你总能自己创造方法！

getMean()

 public double getMean(double[] numberList) { double total; for (double d: numberList) { total += d; } return total / (numberList.length); } 

getMedian()

此方法假设传递的数组已经排序（即{1,2,3，…}）。

 public double getMedian(double[] numberList) { int factor = numberList.length - 1; double[] first = new double[(double) factor / 2]; double[] last = new double[first.length]; double[] middleNumbers = new double[1]; for (int i = 0; i < first.length; i++) { first[i] = numbersList[i]; } for (int i = numberList.length; i > last.length; i--) { last[i] = numbersList[i]; } for (int i = 0; i <= numberList.length; i++) { if (numberList[i] != first[i] || numberList[i] != last[i]) middleNumbers[i] = numberList[i]; } if (numberList.length % 2 == 0) { double total = middleNumbers[0] + middleNumbers[1]; return total / 2; } else { return middleNumbers[0]; } } 

getMode()

 public double getMode(double[] numberList) { HashMap freqs = new HashMap(); for (double d: numberList) { Double freq = freqs.get(d); freqs.put(d, (freq == null ? 1 : freq + 1)); } double mode = 0; double maxFreq = 0; for (Map.Entry entry : freqs.entrySet()) { double freq = entry.getValue(); if (freq > maxFreq) { maxFreq = freq; mode = entry.getKey(); } } return mode; } 

getRange()

 public double getRange(double[] numberList) { double initMin = numberList[0]; double initMax = numberList[0]; for (int i = 1; i <= numberList.length; i++) { if (numberList[i] < initMin) initMin = numberList[i]; if (numberList[i] > initMax) initMax = numberList[i]; } return initMax - initMin; } 

Answer 2

Apache Commons Math会做到这一点。

http://commons.apache.org/math/userguide/stat.html#a1.3_Frequency_distributions