how to use a double value in power function

Question

i am trying to find the power of a value.But the problem is my exponent is a fractional value.power function does not suppporting any datatype other than int.

 BigDecimal fd_returns_at_time_of_replace=(BigDecimal.valueOf(capitalDiff).multiply((BigDecimal.valueOf((long)constant1+.09)).pow(temp)));

here temp is a fractional value.given below is the eror message i am getting.

The method pow(int) in the type BigDecimal is not applicable for the arguments (double)

please anybody help me to do this.

then pass `int` type as argument or type cast `double` to `int`. — Prince John Wesley, Oct 20 '11 at 06:35
possible duplicate http://stackoverflow.com/questions/3579779/how-to-do-a-fractional-power-on-bigdecimal-in-java — spatulamania, Oct 20 '11 at 06:37
no..i want to use the same value.i mean i need that fractional value.i cant round or typecast the value. — andro-girl, Oct 20 '11 at 06:38

score 1 · Accepted Answer · edited May 23 '17 at 12:27

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BigDecimal.pow() only takes an int. To see a cool example of writing BigDecimal.pow() that accepts a double, see this question How to do a fractional power on BigDecimal in Java?

edited May 23 '17 at 12:27

Community

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answered Oct 20 '11 at 06:40

spatulamania

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i read that answer.but i could not understand anything.i am not that familiar with android.can you please simplfy that. – andro-girl Oct 20 '11 at 06:43

score 1 · Answer 2 · answered Oct 20 '11 at 06:52

Common Sense

Consider you want to raise the number x to the power y

If both are integers:

for(int i=0 ; i<y ; i++)
    answer = answer * x;

Problems are only when y is a decimal!

So we first change y to the form of y = n + 1/d

How to do that:

n = floor of y
d = 1 / (y - n) << integer

Now x^y = x^n * x^1/d

x to the power n is simple using the usual method
x to the power 1/d is simply the d th root of x

Note: You can increase the precision of your function by reducing the error factor induced by makind d an integer. How! 1/d can be multiplied by powers of 10.

how to use a double value in power function

2 Answers2