Easy PHP, Radioactivity module: Read out a node's current energy? Sorry, this is a super stupid problem but I'm new to PHP and failed at solving it myself.

On my node I have an energy field (Radioactivity module) and a computed field. The computed field is supposed to read out the node's current energy, plug it into a function and return another value.

I have tried all of

float( $entity->field_energy ),

float( $entity->field_energy[0]['value'] ), and

float( array_pop(array_pop(field_get_items($entity_type, $entity, 'field_energy'))) )

to read out the node's current energy, but everythings gives me an error. When I replace the above with a static number everything works fine.

Can anyone tell me how to read out the energy? I don't even know what data type is used to store the energy.

(I couldn't add a radioactivity tag. Unfortunately I don't have enough reputation points for doing so.)
My guess is that it is something like

float($entity-&gt;field_energy['und'][0]['value']);


Also, you can do 

print_r ($entity-&gt;field_energy);


to see what is contained in object.

also, it may be contained in node object so maybe it is

float($node-&gt;field_energy['und'][0]['value']);


My blind guess but it may help you :)