public int degreesOfFreedom() {
		return buckets.size() - 1;
	}
Return the <em>degrees of freedom</em> of the histogram, which is
{@code buckets().size() - 1}.

@see <a href="https://en.wikipedia.org/wiki/Degrees_of_freedom_(statistics)">
    Degrees of freedom</a>

@return the degrees of freedom
jenetics.incubator/src/main/java/io/jenetics/incubator/stat/Histogram.java