<h3>ymax function</h3>
Returns the maximum y coordinate of a geometry. Calculations are in the Spatial Reference System of this Geometry. 

<h4>Syntax</h4>
<pre>ymax(geom)</pre>

<h4>Arguments</h4>
geom &rarr; a geometry

<h4>Example</h4>
<pre> ymax($geometry) &rarr; returns maximum y coordinate of $geometry</pre>

