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https://issues.apache.org/jira/browse/MATH-1007?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13709321#comment-13709321
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Phil Steitz commented on MATH-1007:
-----------------------------------
I think it is best to return a double[]. Here is what I propose as method
signature / contract:
{code}
/**
* Returns the sample mode(s). The mode is the most frequently occurring
* value in the sample. If there is a unique value with maximum frequency,
* this value is returned in the first element of the output array.
Otherwise,
* the returned array contains the maximum frequency elements in increasing
* order. For example, if {@code sample} is {0, 12, 5, 6, 0, 13, 5, 17},
* the returned array will have length two, with 0 in the first element and
* 5 in the second.
*
* <p>NaN values are ignored when computing the mode - i.e., NaNs will never
* appear in the output array. If the sample includes only NaNs or has
* length 0, an empty array is returned.</p>
*
* @param sample input data
* @return array of maximum frequency elements sorted in ascending order.
*/
public static double[] mode(final double[] sample)
{code}
> Add mode function to StatUtils class
> ------------------------------------
>
> Key: MATH-1007
> URL: https://issues.apache.org/jira/browse/MATH-1007
> Project: Commons Math
> Issue Type: New Feature
> Reporter: Sebb
>
> It might be useful to have a StatUtils function to get the mode.
> However, this may be tricky as it does not easily fit in with the current
> StatUtils design.
> The mode can have multiple elements, but all the other methods only return a
> single value.
> There are at least two options for converting an array to a single value:
> - arbitrarily (or randomly) pick one
> - throw an Exception if there is more than one mode
> Or maybe StatUtils should return a double array.
> StatUtils also uses nested classes for all but the difference and normalize
> methods. However the standard interfaces and classes don't support returning
> arrays.
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