Rilcon42 - 6 months ago 22

Ruby Question

I spent some time trying to find a way to do basic operations on each element in an array such as sum, round, etc.

I didn't see a built-in way to do this, so I tried to create my own after finding "Generic 'sum' And 'mean' Methods For Ruby Arrays".

Can someone explain why my

`round`

`class Array`

def sum

inject(nil) { |sum, x| sum ? sum + x : x }

end

def mean

sum / size

end

def round(p)

inject(nil) { |x| (x * 10 ^ (p-1)).floor / 10 ^ (p - 1) }

end

end

puts [1.1234, 1.45656, 1.546567, 1.4577887].mean

puts [1.1234, 1.45656, 1.546567, 1.4577887].round(6)

Answer

You want the following.

```
class Array
def sum
inject(:+)
end
def mean
sum / size.to_f
end
def round(p)
map { |n| n.round(p) }
end
end
puts [1.1234, 1.45656, 1.546567, 1.4577887].mean
1.3960789249999999
puts [1.1234, 1.45656, 1.546567, 1.4577887].round(6)
1.1234
1.45656
1.546567
1.457789
```

Note that `sum.to_f`

(or `size.to_f`

) is needed when the array contains only integers. If `arr.sum = 3`

and `arr.size = 2`

, `sum / size #=> 1`

whereas `arr.sum / arr.size.to_f #=> 1.5`

.