的JavaScript。 Math.sqrt给NaN一个正数？ [英] Javascript. Math.sqrt giving NaN to a positive number?
问题描述
我目前有一个脚本，它从文本区域获取数字，并使用它们进行各种计算。我的标准偏差功能有问题，因为它不会输出值，即使它的类型是数字，也是正数（.56）。
I currently have a script that takes numbers from a text area and does all sorts of calculations with them. I am having trouble with my standard deviation function because it will not output the value even though it's type is number, and it is positive (.56).
当我运行此代码时
var variance = findVariance(array);
variance = parseFloat(variance);
alert(typeof variance);
结果是
数字
number
值为.56（我知道因为当我不使用parseFloat时它返回.56作为一个字符串）。因此，当我运行此代码时，我感到困惑
And the value is .56 (which I know because when I don't use parseFloat it returns .56 as a string). So I am baffled when I run this code
alert("variance " + variance);
alert("sd" + Math.sqrt(variance));
并且两个警报都返回
NaN
NaN
这是创建textarea的代码，调用函数processData（它将myTextArea的输入收集到一个数组，然后调用函数findStandardDeviation）我也可以发布方差函数。
This is the code that creates the textarea, calls the function processData( which gathers the input from myTextArea into an array and then calls the function findStandardDeviation) I can post the variance function as well if you'd like.
<textarea id="myTextArea" rows = "7" cols = "50"></textarea><br>
<button onclick="processData()">Done</button>
<p id = "sd"></p>
<script type = "text/javascript">
var standard_deviation = 0;
var sdOutput = document.getElementById('sd');
function processData()
{
var arrayOfLines = document.getElementById('myTextArea').value.split('\n');
findStandardDeviation(arrayOfLines);
}
这是我可以管理的最简化的脚本形式：
This is the most reducible form of my script I could manage:
var mean = 0;
var median = 0;
var count = length;
var mode = 0;
var variance = 0;
var standard_deviation = 0;
var meanOutput = document.getElementById('mean');
var countOutput = document.getElementById('count');
var sumOutput = document.getElementById('sum');
var varianceOutput = document.getElementById('variance');
var sdOutput = document.getElementById('sd');
function processData() {
var arrayOfLines = document.getElementById('myTextArea').value.split('\n');
var sum = findSum(arrayOfLines);
findMeanOutput(arrayOfLines, sum);
findVariance(arrayOfLines);
findStandardDeviation(arrayOfLines);
}
function findSum(array) {
var count = array.length;
var sum = 0;
for (var a = 0; a < array.length; a++) {
sum += parseInt(array[a]);
}
countOutput.innerHTML = "Count: " + array.length;
sumOutput.innerHTML = "Sum: " + JSON.stringify(sum);
sum = parseInt(sum);
return sum;
}
function findMean(array) //Used for finding mean and then returning it
{
var sum = 0;
for (var a = 0; a < array.length; a++) {
sum += parseFloat(array[a]);
}
mean = sum / array.length;
return mean;
}
function findMeanOutput(array, sum) //finds mean and then establishes it as the mean for users input
{
mean = sum / array.length;
meanOutput.innerHTML = "Mean: " + mean;
}
function findVariance(array) {
var mean = findMean(array);
var variance = "Variance: " + findMean(array.map(function(num) {
return Math.pow(num - mean, 2);
})).toFixed(2);
varianceOutput.innerHTML = "Variance: " + variance;
return variance;
}
function findStandardDeviation(array) {
var variance = findVariance(array);
variance = parseFloat(variance);
alert(typeof variance);
alert("variance " + variance);
alert("sd" + Math.sqrt(variance));
sdOutput.innerHTML = "Standard Deviation: " + Math.sqrt(variance).toFixed(2);
}
<html>
<head>
</head>
<body>
<p> Please enter a series of numbers, each separated by a new line.<br>
<p>
<textarea id="myTextArea" rows="7" cols="50"></textarea><br>
<button onclick="processData()">Done</button>
<p id="mean"></p>
<p id="count"></p>
<p id="sum"></p>
<p id="variance"></p>
<p id="sd"></p>
</body>
</html>
推荐答案
.56 不是整数，所以你不应该使用 parseInt函数。 parseFloat 是您正在寻找的功能。或者更简单：数字。
.56 is not an integer, so you shouldn’t use parseInt. parseFloat is the function you’re looking for. Or much simpler: Number.
这篇关于的JavaScript。 Math.sqrt给NaN一个正数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
