Rails: bad math?

Question

I've got this method:

def progress_percentage
  (progress_index / positive_statuses.size) * 100
end

It's returning 0 and it should be 38.46.

@lead.progress_index          # this is 5
@lead.positive_statuses.size  # this is 13
@lead.progress_percentage     # this is 0?

The first two values have been confirmed. What is going on? Edit: confirmed in the view here.

the duplicate doesn't cover rounding to two places. – Sagar Pandya Nov 02 '16 at 01:20 — Sagar Pandya, Nov 02 '16 at 01:20

score 5 · Accepted Answer · answered Nov 02 '16 at 00:40

5

Welcome to integer math. In Ruby (like many languages) an integer divided by an integer returns an integer. In your case, 5 / 13 returns 0. If either your numerator or denominator is converted to a float before you run this operation, you will get a float in return, and the expected answer will result.

You can convert to a float using to_f. So (progress_index.to_f / positive_statuses.size) * 100 should work.

answered Nov 02 '16 at 00:40

moveson

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Ah. Integers. Of course. Thanks for the deep answer. – t56k Nov 02 '16 at 00:54

score 0 · Answer 2 · edited Jun 20 '20 at 09:12

0

You can use Fixnum#fdiv and Float#round here:

def progress_percentage
  ((progress_index.fdiv positive_statuses.size) * 100).round 2
end

as requested, returns your number rounded to two decimal places.

Example

((5.fdiv 13)*100).round 2
#=> 38.46

edited Jun 20 '20 at 09:12

Community

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answered Nov 02 '16 at 00:44

Sagar Pandya

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Rails: bad math?

2 Answers2

Example