[R] number of decimal

[Ivan Calandra]

First things first: thanks for your help!

I see where the confusion is. With formatC and sprintf, I have to store 
the numbers I want to change into x.

I would like a way without applying a function on specific numbers 
because I can shorten the numbers that way, but it won't give me more 
decimals for a test for example.
What I mean here is that if I have a F-value = 1.225, formatC won't give 
me the next 3 decimals, it will just add zeros.
I need that because for some of my variables, the sample differ only at 
the 6th decimal (0.000005 vs 0.000006), and for other ones the order of 
magnitude is much higher (120.120225 vs 210.665331). So 
options(digits=6) cannot do the job as I would like. To make myself even 
clearer, notice that in my example, all numbers have 6 decimals, but a 
different number of digits.

I hope I'm not bothering you with this question, but I believe that the 
functions you advised me will not do what I need.
I really need something that will set up the number of decimals by 
default, before the numbers are created by any function.
Does such an option even exist in R? Or is it that it doesn't make sense 
to have different numbers of digits? Would it be better to compare 
0.000005 and 210.665? Therefore options(digits=6) would be enough.

Regards,
Ivan

Le 1/28/2010 16:43, Peter Ehlers a écrit :
> Ivan Calandra wrote:
>> It looks to me that it does more or less the same as format().
>>
>> Maybe I didn't explain myself correctly then. I would like to set the 
>> number of decimal by default, for the whole R session, like I do with 
>> options(digits=6). Except that digits sets up the number of digits 
>> (including what is before the "."). I'm looking for some option that 
>> will let me set the number of digits AFTER the "."
>>
>> Example: I have 102.33556677 and 2.999555666
>> If I set the number of decimal to 6, I should get: 102.335567 and 
>> 2.999556.
>> And that for all numbers that will be in/output from R (read.table, 
>> write.table, statistic tests, etc)
>>
>> Or is it that I didn't understand everything about formatC() and 
>> sprintf()?
> You didn't:
>
> formatC(x, digits=6, format="f")
> [1] "102.335567" "2.999556"
>
> sprintf("%12.6f", x)
> [1] "  102.335567" "    2.999556"
>
>  -Peter Ehlers
>
> >
>>
>> Thanks again
>> Ivan
>>
>> Le 1/28/2010 15:12, Peter Ehlers a écrit :
>>> ?formatC
>>> ?sprintf
>>>
>>> Ivan Calandra wrote:
>>>> Hi everybody,
>>>>
>>>> I'm trying to set the number of decimals (i.e. the number of digits 
>>>> after the "."). I looked into options but I can only set the total 
>>>> number of digits, with options(digits=6). But since I have 
>>>> different variables with different order of magnitude, I would like 
>>>> that they're all displayed with the same number of decimals.
>>>> I searched for it and found the format() function, with nsmall=6, 
>>>> but it is for a given vector. I would like to set it for the whole 
>>>> session, as with options.
>>>>
>>>> Can anyone help me?
>>>> Thanks in advance
>>>> Ivan
>>>>
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>>
>>
>