how to get nearest tenth of a double

Question

I want to round up double number in java such that it converts to it's nearest tenth like below..

0.1--->0.1
0.3--->1
1----->1
1.5---->10
92---->100
4.0E8-->1.0E9
etc

How can I do it Actually my intention is to set Y-axis on chart, if max value is 0.1 then num_ spacing will set to .01 if it is .3 then convert to 1 then set num_ spacing to .1 and so on

because 0.1 is 1/10, he wants to reach the next tenth value, not the logical rounding. — SomeJavaGuy, Dec 19 '12 at 11:46
The rounding sequence looks weird. `|0.3 - 0.1| < |0.3 - 1|`. Why is 0.3 rounded to 1? — svz, Dec 19 '12 at 11:48
actually it is to set Y-axis on chart, if max value if 0.1 then num_ spacing will set to .01 if it is .3 then convert to 1 then set num_ spacing to .1 and so on — agarwal_achhnera, Dec 19 '12 at 11:49
Doubles can't represent all tenths precisely. You can round to the nearest double of the nearest tenth though. — COME FROM, Dec 19 '12 at 12:03
possible duplicate of [How to round a number to n decimal places in Java](http://stackoverflow.com/questions/153724/how-to-round-a-number-to-n-decimal-places-in-java) — starblue, Dec 23 '12 at 22:18

score 10 · Accepted Answer · answered Dec 19 '12 at 11:49

10

Try translating this into your language, I've written it in Matlab but it ought to be obvious

10^ceil(log10(x))

Of course, this will only work if x is positive.

answered Dec 19 '12 at 11:49

High Performance Mark

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1

In Java, it's: `Math.pow(Math.ceil(Math.log10(x)), 10)` – Codo Dec 19 '12 at 11:54
2

Actually the exponent is the second argument: `Math.pow(10, Math.ceil(Math.log10(x)));` – VGR Dec 19 '12 at 11:58
@VGR: Thanks for spotting it. – Codo Dec 19 '12 at 12:02
To round down, replace `ceil` with `floor`. – ggkmath Jul 17 '13 at 00:39

score 0 · Answer 2 · answered Dec 19 '12 at 11:53

0

you can have a look..

              double a = 120.1;
    double last_digit_rem = 10 - (a % 10);
    System.out.println(a+last_digit_rem);

It will work for negative numbers also...

answered Dec 19 '12 at 11:53

Srinivas B

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I think the result should be 1000 in this case not 130 – SomeJavaGuy Dec 19 '12 at 11:56
No... It is 0.09999999999999432, so, 10-(a%10) will be 9.900000000000006, final result would be 130.0 – Srinivas B Dec 19 '12 at 11:58

how to get nearest tenth of a double

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