# Genetic Algorithms in Elixir:P67 fitness\_function correction

**URL:** <https://forum.devtalk.com/t/genetic-algorithms-in-elixir-p67-fitness-function-correction/10027>\
**Category:** PragProg Customers\
**Tags:** book-genetic-algorithms-in-elixir, errata\
**Created:** [30 May 2021 14:57 UTC](https://forum.devtalk.com/t/genetic-algorithms-in-elixir-p67-fitness-function-correction/10027 "2021-05-30T14:57:28Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![adkelley](https://forum.devtalk.com/user_avatar/forum.devtalk.com/adkelley/32/2873_2.png) [@adkelley](https://forum.devtalk.com/u/adkelley)\
**Post date:** [30 May 2021 14:57 UTC](https://forum.devtalk.com/t/genetic-algorithms-in-elixir-p67-fitness-function-correction/10027/1 "2021-05-30T14:57:28Z")

</div>

```auto
def fitness_function(chromosome) do
   chromosome
   |> Enum.map(fn {roi, risk} -> 2 * roi - risk end) 
   |> Enum.sum()
end

```

should be:

```auto
def fitness_function(chromosome) do
  chromosome.genes
  |> Enum.map(fn {roi, risk} -> 2 * roi - risk end) 
  |> Enum.sum()
end

```