我想从我的数组中获取中位数长度。我使用以下代码,但我收到错误。我不知道为什么会出现这些错误。
int middleSlot = list.length/2;
list[middleSlot];
答案 0 :(得分:0)
Apache Commons Math会这样做。
http://commons.apache.org/proper/commons-math/userguide/stat.html#a1.3_Frequency_distributions
OR: Mean, Median, Mode, Range - Java
使用方式为:
double answer = getMean(list);
<强> getMean()强>
public double getMean(double[] numberList) {
double total;
for (double d: numberList) {
total += d;
}
return total / (numberList.length);
}
<强> getMedian()强>
This method is going on the assumption that the passed array is already sorted (i.e. {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];
}
}
<强>获取模式()强>
public double getMode(double[] numberList) {
HashMap<Double,Double> freqs = new HashMap<Double,Double>();
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<Double,Doubler> entry : freqs.entrySet()) {
double freq = entry.getValue();
if (freq > maxFreq) {
maxFreq = freq;
mode = entry.getKey();
}
}
return mode;
}
<强> getRange()强>
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;
}
答案 1 :(得分:0)
要将元素放在中间,您可能需要执行类似
的操作int middleSlot = list.size()/2;
int counter =0 ;
TypeOfList middleElement=null;
for(TypeOfList eachElement: list.values) {
if(counter == middleSlot) {
middleElement= eachElement; break;
}
counter++;
}