[R] number of decimal

[Ivan Calandra]

Hi,

Actually, I have two steps, the first would be to import a csv file 
(read.csv). There I would need to have the same number of decimals as 
there are on the original file.
Then I would run some analyses and probably export the results, e.g. 
ANOVA table (write.csv). Here too I would like to have a sufficiently 
large number of decimals (usually 6).
I think it shouldn't be too problematic to export correctly, I could set 
up the number of decimals using format(), since the object is stored 
internally (though I will have to figure out for each test how to get to 
the test and p-values). I usually don't use these values again, I just 
need to print them. From what I've tested, it even seems that the full 
precision is also exported!

And it looks like the importing save internally all decimals from the 
input file.

So actually, it looks like it was just about the display. I didn't 
expect that the printing and internal handling of numbers would be 
different. I thought that the tests would be computed using the printed 
values. But if it uses the full precision, then everything is fine.

All that because of the printing! It's probably a newbie 
misunderstanding :-)
Thanks a lot for all your help!
Ivan


Le 1/28/2010 17:36, Peter Ehlers a écrit :
> Ivan,
>
> Now I'm no longer sure of just what you want. Are you concerned about
> the *internal* handling of numbers by R or just about the *printing*
> of numbers? As Marc has pointed out, internally R will use the full
> precision that your input allows.
>
> Perhaps you're using the F-value from the output of a
> procedure like aov() as input to further analysis. If so,
> don't use the printed value; pull the value out of the
> object with something like
>
>  fm <- aov(y ~ x)
>  Fval <- summary(fm)[[1]][1,4]
>
> But maybe this is not at all what you're after.
>
>  -Peter Ehlers
>
> Ivan Calandra wrote:
>> 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
>>>>>>
>>>>>> ______________________________________________
>>>>>> R-help at r-project.org mailing list
>>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>>> PLEASE do read the posting guide 
>>>>>> http://www.R-project.org/posting-guide.html
>>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>>
>>>>>>
>>>>
>>>>
>>>
>>
>>
>