How do I register my custom UDF so I can run it in spark-shell
<p>I defined the following custom UDF:</p>

<pre><code>def stddev1 (columnName: Column): Column = {
    sqrt(avg(columnName * columnName) - avg(columnName) * avg(columnName))
}
</code></pre>

<p>I want to run this function in spark-shell and test it with some example data but I keep running into errors: "Schema for type org.apache.spark.sql.Column is not supported."</p>

<p>I might have to register it but I'm unsure how to do this</p>