meru-akimbo/gist:2902179

## gistfile1.js
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
<link href="./css/index.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {

    $("#enzan").click( function() {
        var a = $("#start").val();
        var b = $("#end").val();
        var fx = $("#siki").val();
        var n = 10000;

        var s;

        if( jQuery.isNumeric(a) || jQuery.isNumeric(b) )
        {
            a = Number(a);
            b  =Number(b);
            var h = ( b - a ) / (2*n);

            var i=0;
            x = new Array(2*n+1);
            xx = new Array(2*n+1);
            y = new Array(2*n+1);
            yy=0;

            var fxx;

            while(i <= 2*n)
            {
                x[i] = (a+h*i);
                i++;
            }
            i = 0;

            fxx = fx.replace(/x/g, "x[i]");

            while(i <= 2*n)
            {
                y[i] = eval(fxx);
                i++;
            }

            i = 0;

            while(i<=(2*n))
            {
                if( i == 0 || i == 2*n)
                {
                    yy = yy + y[i];
                }
                else if( i % 2 == 1)
                {
                    yy = yy + 4*y[i];
                }
                else
                {
                    yy = yy + 2*y[i];
                }

                i++;
            }

            s = h/3 * yy;
            $("#kekka").html("<font size='4'><b>S="+s+"</b></font>");

        }
        else
        {
            alert("範囲が数値でない");
        }


    });
});
</script>
</head>
<body>
<table border="5">
  <tr>
     <td><font size="5"><b>シンプソン法での定積分</b></font></td>
  </tr>
  <tr>
     <td>始点：a  <input type="text" value="a" id="start" /></td>
  </tr>
  <tr>
     <td>終点：b  <input type="text" value="b" id="end" /></td>
  </tr>
  <tr>
     <td>関数：f(x)  <input type="text" value="f(x)" id="siki" /></td>
  </tr>
  <tr>
     <td><button id="enzan" />計算</button></td>
  </tr>
    <tr>
     <td><span id="kekka" /></td>
  </tr>
</table>

</body>
</html>
	<html>
	<head>
	<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
	<link href="./css/index.css" rel="stylesheet" type="text/css" />
	<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
	<script type="text/javascript">
	$(document).ready(function() {

	$("#enzan").click( function() {
	var a = $("#start").val();
	var b = $("#end").val();
	var fx = $("#siki").val();
	var n = 10000;

	var s;

	if( jQuery.isNumeric(a) \|\| jQuery.isNumeric(b) )
	{
	a = Number(a);
	b =Number(b);
	var h = ( b - a ) / (2*n);

	var i=0;
	x = new Array(2*n+1);
	xx = new Array(2*n+1);
	y = new Array(2*n+1);
	yy=0;

	var fxx;

	while(i <= 2*n)
	{
	x[i] = (a+h*i);
	i++;
	}
	i = 0;

	fxx = fx.replace(/x/g, "x[i]");

	while(i <= 2*n)
	{
	y[i] = eval(fxx);
	i++;
	}

	i = 0;

	while(i<=(2*n))
	{
	if( i == 0 \|\| i == 2*n)
	{
	yy = yy + y[i];
	}
	else if( i % 2 == 1)
	{
	yy = yy + 4*y[i];
	}
	else
	{
	yy = yy + 2*y[i];
	}

	i++;
	}

	s = h/3 * yy;
	$("#kekka").html("<font size='4'><b>S="+s+"</b></font>");

	}
	else
	{
	alert("範囲が数値でない");
	}


	});
	});
	</script>
	</head>
	<body>
	<table border="5">
	<tr>
	<td><font size="5"><b>シンプソン法での定積分</b></font></td>
	</tr>
	<tr>
	<td>始点：a <input type="text" value="a" id="start" /></td>
	</tr>
	<tr>
	<td>終点：b <input type="text" value="b" id="end" /></td>
	</tr>
	<tr>
	<td>関数：f(x) <input type="text" value="f(x)" id="siki" /></td>
	</tr>
	<tr>
	<td><button id="enzan" />計算</button></td>
	</tr>
	<tr>
	<td><span id="kekka" /></td>
	</tr>
	</table>

	</body>
	</html>