Re: [R] apply min function rowwise

From: Joshua Wiley <jwiley.psych_at_gmail.com>
Date: Sat, 05 Jun 2010 11:11:50 -0700

On Sat, Jun 5, 2010 at 10:22 AM, moleps <moleps2_at_gmail.com> wrote:
> thx.
>
> It was only the first instance that was class date. The rest were factors. So that explains it.
>
> If I want to change the rest in vec into class date (there are many of them...)
>
> neither  as.Date(canc[,vec],"%d.%m.%Y") or sapply(canc[,vec],FUN=function(x) as.date(x,"%d.%m.%Y"))
>
> What is the easy solution to this?

This is the nicest solution that comes to mind:

as.data.frame(lapply(X=samp.dat, FUN=as.Date, format="%d.%m.%Y"))

I believe the problem is that sapply() coerces the results (by default when simplify=TRUE) using as.vector() leaving you with the number of days since the origin. Anyway, using as.data.frame() on the list output from lapply() seems to work.

Josh

>
> Regards,
>
> //M
>
>
>
> On 5. juni 2010, at 18.30, Joshua Wiley wrote:
>
>> Hello M,
>>
>> My guess is that it has something to do with the class of the
>> variables.  Perhaps you could provide a small sample dataframe?  Also
>> you might try running str() on your data frame and seeing if the
>> results are what you would expect.  As a side note, it is not
>> necessary to make an anonymous function here, as you are allowed to
>> pass arguments to the function applied.
>>
>> apply(canc[,vec],1, min, na.rm=TRUE)
>>
>> Best regards,
>>
>> Josh
>>
>> On Sat, Jun 5, 2010 at 8:30 AM, moleps <moleps2_at_gmail.com> wrote:
>>> I´m trying to tease out the minimum value from a row in a dataframe where all the variables are dates.
>>>
>>> apply(canc[,vec],1,function(x)min(x,na.rm=T))
>>>
>>>
>>> However it only returns empty strings for the entire dataframe except for one date value (which is not the minimum date).
>>>
>>> I´ve also tried
>>>
>>> apply(canc[,vec],1,function(x)max(x,na.rm=T))
>>>
>>> which provides values rowwise, but many of them are not in fact the largest in the row.
>>>
>>>
>>> Any advice?
>>>
>>>
>>> Regards,
>>>
>>> //M
>>>
>>> ______________________________________________
>>> 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.
>>>
>>
>>
>>
>> --
>> Joshua Wiley
>> Senior in Psychology
>> University of California, Riverside
>> http://www.joshuawiley.com/
>
>

-- 
Joshua Wiley
Senior in Psychology
University of California, Riverside
http://www.joshuawiley.com/

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Received on Sat 05 Jun 2010 - 18:13:45 GMT

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