Using Arcade to count nulls or non-nulls from an array

GeorgeClutterbuck

Hi,

I am trying to transfer some code I use in python to arcade in order to take advantage of the attribute rule calculation. I currently have some python that calculates the average of an array but discounts null values if it finds them in the array. I'm looking to use arcade to count how many nulls or non-nulls there are... the Count function or the isEmpty function don't seem suited.

The last best code which isn't working (so best isn't great!) is:

var array = [$feature.Welcoming,$feature.Access];
var count = [i for i in array if i];
'Sum(array) / float(count)'

Any help would be great thanks!

XanderBakker

Hi Jim Phillips ,

Have a look at the snippet below:

<SPAN class="keyword token">var</SPAN> arr <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="keyword token">null</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">3</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="token function">Console</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"sum :"</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="token function">Sum</SPAN><SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="token function">Console</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="string token">"mean:"</SPAN> <SPAN class="operator token">+</SPAN> <SPAN class="token function">Mean</SPAN><SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">;</SPAN>

<SPAN class="keyword token">var</SPAN> tot <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="keyword token">var</SPAN> cnt <SPAN class="operator token">=</SPAN> <SPAN class="number token">0</SPAN><SPAN class="punctuation token">;</SPAN>
<SPAN class="keyword token">for</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="keyword token">var</SPAN> i <SPAN class="keyword token">in</SPAN> arr<SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
    <SPAN class="keyword token">if</SPAN> <SPAN class="punctuation token">(</SPAN><SPAN class="operator token">!</SPAN><SPAN class="token function">IsEmpty</SPAN><SPAN class="punctuation token">(</SPAN>arr<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="punctuation token">{</SPAN>
        tot<SPAN class="operator token">+</SPAN><SPAN class="operator token">=</SPAN>arr<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">;</SPAN>
        cnt<SPAN class="operator token">+</SPAN><SPAN class="operator token">=</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">;</SPAN>
    <SPAN class="punctuation token">}</SPAN>
<SPAN class="punctuation token">}</SPAN>

<SPAN class="keyword token">var</SPAN> promedio <SPAN class="operator token">=</SPAN> tot<SPAN class="operator token">/</SPAN>cnt<SPAN class="punctuation token">;</SPAN>
<SPAN class="keyword token">return</SPAN> promedio<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>‍</SPAN><SPAN>‍</SPAN></SPAN>

I have an array with 3 values, of which 1 is null. When I use the Sum it will return a correct result, since 1+null+3 = 4. The Mean however will not return the correct result, since the sum 4 will be divided by 3 elements and return 1.333.

To avoid this, you will probably have to loop through the array and only cnt and sum the non-null values. In Arcade you cannot use the list comprehensions that you are showed in your example.