mean(columnName) {
        const numericDF = this.df.filter(row => isNumber(row.get(columnName)));
        return (
            Number(
                numericDF.reduce(
                    (p, n) =>
                        isNumber(n.get(columnName))
                            ? p + Number(n.get(columnName))
                            : p,
                    0
                )
            ) / numericDF.count()
        );
    }
Compute the mean value into a numeric column.
@param {String} columnName The column to evaluate,isNumber(n.get(columnName)) ? p + Number( containing Numbers.
@returns {Number} The mean value into the column.
@example
df.stat.mean('column1')