ruby round off to two decimal place and keep zero

Question

i want to round off a number upto two decimal place in ruby such that

(0.02 * 270187).round(2) is 5403.74 which is correct

but

(0.02 * 278290).round(2) is 5565.8 which is not consistent with previous one

i want to make it look like 5565.80

Please tell me how can i do it in ruby

Solution 1

This will do the trick:

> sprintf("%.2f",(0.02 * 270187))
#=> "5403.74" 
> sprintf("%.2f",(0.02 * 278290))
#=> "5565.80"
> sprintf("%.2f",(0.02 * 270187)).to_f > 100  # If you plan to Compare something with result
#=> true 

OR

> '%.2f' % (0.02 * 270187)
#=> "5403.74"
> '%.2f' % (0.02 * 278290)
#=> "5565.80" 

Demo

Note: The result is always a string, but since you're rounding I assume you're doing it for presentation purposes anyway. sprintf can format any number almost any way you like. If you are planning to compare anything with this result then convert this string to float by adding .to_f at the end. Like this

Solution 2

You could do something like

include ActionView::Helpers::NumberHelper

number_with_precision(value, :precision => 2) # value.to_f if you have string

or like this

'%.2f' % your_value

Hope it helps! Further you can read from here

Comments

[user4965201]

i am getting ArgumentError (comparison of String with 0 failed) ... i am using this method in rails

[Dusht]

You can convert your string to float like value.to_f

[user4965201]

i am getting some value as 0, think thats why i am getting the error

[Dusht]

Can you please provide your code, where you are actually using it.

[user4965201]

cost = number_with_precision((to_mb(monthly_usage) * cost_per_mb).to_f, :precision => 2)

[user4965201]

getting this error ArgumentError (comparison of ActiveSupport::SafeBuffer with 0 failed):

[Dusht]

I am assuming, you are getting correct values from to_mb(monthly_usage) and cost_per_mb. Also have you included include ActionView::Helpers::NumberHelper ? Can you please also try with '%.2f' % (to_mb(monthly_usage) * cost_per_mb)

[user4965201]

Let us continue this discussion in chat.

[user4965201]

i am getting this error ArgumentError (comparison of String with 0 failed):

[Gagan Gami]

@user4965201 : as I already said it will return as string. and you are trying to compare something with this result further

[Gagan Gami]

@user4965201 : If you wanted to compare then add .to_f at the end. check

[user4965201]

i have done this cost = ('%.2f' % (to_mb(monthly_usage) * cost_per_mb)).to_f but i got a record like 5565.8 , no zero at the end

[Dusht]

@user4965201 You can do cost = ('%.2f' % (to_mb(monthly_usage) * cost_per_mb)).to_f

[Gagan Gami]

what is value of monthly_usage and cost_per_mb and what is to_mb(monthly_usage)

[Gagan Gami]

do it like ('%.2f' % ((to_mb(monthly_usage) * cost_per_mb)).to_f )

[Gagan Gami]

@user4965201 ('%.2f' % ( 0.02 * 278290).to_f) this will return "5565.80"

[user4965201]

but i want it as 5565.80 when i do "5565.80".to_f it gives 5565.8

[Gagan Gami]

to_f will remove last zero after . so if it is 1.20 become 1.2 and 1.23 will remain same.