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I have latitude and longitude values in my database out to 10 decimal places:
+----+---------------+-----------------+
| id | lat | lng |
+----+---------------+-----------------+
| 55 | 34.4208305000 | -119.6981901000 |
| 56 | 30.2671530000 | -97.7430608000 |
I need to query the db for a match, but my current variable is a float with only 6 decimal places:
self.lat => 30.267153
How can I convert my float to have the extra decimal places so I get a match?
myloc = Marker.where("lat = ?", self.lat)
I've seen Decimal and BigDecimal docs. Are those the best approach?
Ruby 1.8.7, Rails 3. Thanks for any advice.
778
The round() method can be used to round a number to a specified number of decimal places in Ruby. We can use it without a parameter ( round() ) or with a parameter ( round(n) ).
Example: # Ensure we store z as a float by making one of the numbers a float. z = 1/3.0 # Format the float to a precision of three. format('%<num>0.3f', num: z) # => "0.333" format('%<num>0.5f', num: z) # => "0.33333" # Add some text to the formatted string format('I have $%<num>0.2f in my bank account.
Ruby | Numeric round() function The round() is an inbuilt method in Ruby returns a number rounded to a number nearest to the given number with a precision of the given number of digits after the decimal point. In case the number of digits is not given, the default value is taken to be zero.
If you want to round down to nth decimal number, multiple ( 10^n ) and round down and divide it by ( 10^n ). Ruby def dec_floor(num, n) 1.upto(n) do num *= 10 end num.floor 1.upto(n) do num /= 10 end end
The round () is an inbuilt method in Ruby returns a number rounded to a number nearest to the given number with a precision of the given number of digits after the decimal point. In case the number of digits is not given, the default value is taken to be zero.
If we want to format the decimal places of one specific number (or a vector of numbers), we can use the format function in combination with the round function and the specification nsmall. Consider the following R syntax: format ( round ( x, 3), nsmall = 3) # Apply format function # "10.766".
Round a number down by using the ROUNDDOWN function. It works just the same as ROUND, except that it always rounds a number down. For example, if you want to round down 3.14159 to three decimal places: =ROUNDDOWN (3.14159,3) which equals 3.141
You can use sprintf—or it's simpler brother String#%—to format your floating point number as a string with 10 decimals:
f = 30.267153
s = "%0.10f" % f
#=> "30.2671530000"
This seems fishy to me, though; what types of fields are your lat and lng columns? What RDBMS are you using? Do you really want to be comparing floating point values exactly? Do you really want to be storing them as strings?
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