Decimal format like 2.07619048e-05

[Richard Cook]

Hi All,

I wonder if you could help me, I have to output an XML file which has lots of decimal values at a certain length.

I have tried DecimalFormat, but I think I am loosing precision, i'm not sure.

The format required is: 2.07619048e-05 etc with all values the same length.

Please could somebody help as I am pulling my hair out!

Thanks in advance.


Regards




Richard

[Jesper de Jong]

In what kind of way is your data stored, as float or double values, or something else?

Can you tell us in more detail (with some code, if possible) what you tried with DecimalFormat and why exactly you think you are loosing precision (do you have an example which shows this)?

[Richard Cook]

Hi Jasper,

Thank you for your prompt reply.

The values are coefficients calculated on the fly using doubles.

The DevimalFormat code is as follows:

    public double roundToDecimals(double d, int c) {
        int temp = (int) ((d * Math.pow(10, c)));
        return (((double) temp) / Math.pow(10, c));
    }

And it is currently called like:

    public double getValue() {
        return roundToDecimals(value, 8);
    }

The format I am trying to match is as follows:

<data type = "Density">
<point name="a1">   2.07619048e-05</point>
<point name="b1">   7.51047619e-03</point>
<point name="c1">   5.80000000e-02</point>
<point name="a2">   3.02095238e-04</point>
<point name="b2">  -2.06228571e-02</point>
<point name="c2">   7.61333333e-01</point>
</data>

But I am getting the following output (ignoring indentation):

                    <data type="Density">
                        <point name="a1">6.9E-6</point>
                        <point name="b1">0.01112619</point>
                        <point name="c1">0.0</point>
                        <point name="a2">1.5023E-4</point>
                        <point name="b2">-0.00320714</point>
                        <point name="c2">0.35833333</point>
                    </data>

I am not completely sure if I am loosing precision, but I would prefer if the values were all in the same format as the above example.

Many thanks


Richard

[Richard Cook]

I was also using:

    DecimalFormat format = new DecimalFormat("0.0000000");

I also changed the 00 for hashes.

Regards



Richard

[James Sabre]

Does this help ?

       double[] values =
        {
            2.07619048e-05,
            7.51047619e-03,
            5.80000000e-02,
            3.02095238e-04,
            -2.06228571e-02,
            7.61333333e-01,
        };
        for (double v : values)
        {
            String formattedV = String.format("%18.8e", v);
            System.out.println("[" + formattedV + "]");
        }

[Richard Cook]

Hi James,

I have just tested that with various long numbers and it is spot on, thank you so much.


Regards



Richard

[James Sabre]

Richard Cook wrote:

I have just tested that with various long numbers and it is spot on, thank you so much.

I'm sceptical of your requirement for such a rigid format inside the XML. XML holds data and should not really care about the formatting of the values it holds. Only views of the XML data should be concerned with the format of displayed numbers.

[Richard Cook]

Hi James,

The reason behind this is the XML is imported in a (not very well written) system, and it was falling over with length issues, hence I wanted to get it as close to the original template as possible.

Thanks again


Richard