How do I write an expression to label the max value for a specific location?

pokateo_

I have a dataset with co-located points (e.g. "Site 1" has 3 rows with different numbers in the Value field). 

I need to label the site with the max value of the set (the highlighted values below).

Anonymous User

Here is a solution using python based on Label highest values and How To: Label a related table 

<SPAN class="keyword token">import</SPAN> arcpy
lyrName <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'path\to\layer'</SPAN>

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">getMax</SPAN><SPAN class="punctuation token">(</SPAN>location<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    filter <SPAN class="operator token">=</SPAN> f<SPAN class="string token">"Location_Name = '{location}'"</SPAN>
        
    <SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN>lyrName<SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="string token">'Value'</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">,</SPAN> where_clause<SPAN class="operator token">=</SPAN>filter<SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>  
        max_val <SPAN class="operator token">=</SPAN> max<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
    <SPAN class="keyword token">return</SPAN><SPAN class="punctuation token">(</SPAN>max_val<SPAN class="punctuation token">)</SPAN>
            
            
<SPAN class="keyword token">def</SPAN> FindLabel <SPAN class="punctuation token">(</SPAN> <SPAN class="punctuation token">[</SPAN>Location_Name<SPAN class="punctuation token">]</SPAN> <SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">return</SPAN> getMax<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN>Location_Name<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

You use a search cursor to find the maximum of all 'Value' for the records where 'Location_Name' matches the Location_Name for the current feature. Be sure to replace the path to your layer (it must be the full path to the data on disc). Since it is reading the data from disk it will not honor things like definition queries so watch out for that. You may also want to disable duplicate labels for the layer.