Hi, Mikkel
I'm using commons-math 2.2. The code to reproduce the issue.
import org.apache.commons.math.stat.descriptive.SummaryStatistics;
import org.apache.commons.math.stat.descriptive.moment.Variance;
@Test public void testStandardDeviation() {
int[] scores = {1, 2, 3, 4};
SummaryStatistics stats = new SummaryStatistics();
stats.setVarianceImpl(new Variance(false)); //use "population variance"
for(int i : scores) {
stats.addValue(i);
}
double sd = stats.getStandardDeviation();
System.out.println(sd);
}
Regards,
Warren Tang <http://blog.tangcs.com>
On 10/16/2011 10:43 PM, Mikkel Meyer Andersen wrote:
Dear Warren,
Could you provide values for the scores-variable in the current
example making it possible to reproduce?
Are you in fact using version 1.2 as reflected by the link you gave?
Or which version are you using?
Cheers, Mikkel.
2011/10/16 Warren Tang<[email protected]>:
Hello, everyone
I'm trying to get a "population standard deviation
<http://commons.apache.org/math/api-1.2/org/apache/commons/math/stat/descriptive/moment/StandardDeviation.html>"
(non-bias-corrected) from SummaryStatistics.
This is what I did:
SummaryStatistics stats = new SummaryStatistics();
stats.setVarianceImpl(new Variance(false)); //use "population variance"
( sum((x_i - mean)^2) / n )
for(int i : scores) {
stats.addValue(i);
}
double sd = stats.getStandardDeviation();
However, the value of "sd" is "NaN". How can I do it correctly?
--
Regards,
Warren Tang<http://blog.tangcs.com>
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
