func CountIdx(ix *etable.IdxView, colIdx int) []float64 {
	return ix.AggCol(colIdx, 0, CountFunc)
}
/////////////////////////////////////////////////
Count
CountIdx returns the count of non-Null, non-NaN elements in given
IdxView indexed view of an etable.Table, for given column index.
Return value is size of each column cell -- 1 for scalar 1D columns
and N for higher-dimensional columns.
package agg
import (
	"math"
	"github.com/emer/etable/etable"
)
type IdxViewAggFuncIdx func(ix *etable.IdxView, colIdx int) []float64
type IdxViewAggFunc func(ix *etable.IdxView, colIdx int) []float64
type IdxViewAggFuncTry func(ix *etable.IdxView, colIdx int) ([]float64, error)