How do I fix this ?

function pool_volume = A09_poolSubfunction_erastogi(surface_r, bottom_r, depth_shallow, depth_deep)
if (surface_r<0||bottom_r<0||depth_shallow<0||depth_deep<0) % calculation limitations
    fprintf('Invalid input \n')
    return
end
%calculating total volume of the pool
part_1= (2*pi*surface_r*depth_shallow);
part_2= (pi*(depth_deep-depth_shallow)*((surface_r)^2+(surface_r*bottom_r)+(bottom_r)^2)/3);
total_volume = (part_1+part_2)*7.48052; % total volume and conversion from feet^3 to gallons
fprintf(' The volume of the pool is % gallons \n',total_volume)
end

%Output argument "pool_volume" (and maybe others) not assigned during call to "A09_poolSubfunction_erastogi".
%this is an error im seeing while i run it

[per isakson]

Rename total_volume to pool_volume ;(

Answer 1

[madhan ravi]

function total_volume = A09_poolSubfunction_erastogi(surface_r, bottom_r, depth_shallow, depth_deep)

Answer 2

[Steven Lord]

In addition to the output argument renaming others have suggested, as written you need to assign something to the output argument in the case where your function was called with invalid input. Otherwise you'll receive this same error in that case. Often NaN is used as an indicator that something went wrong.

Alternately I would probably throw an error (or maybe replace that if statement with four assert statements, if I wanted to throw more specific error messages like "surface_r must be nonnegative") instead of using fprintf and return.