[R] invalid type error

[Joshua Wiley]

Just to clarify, "it" referred to Jason's (OP's) original code and
question, not Erik's solution.

"Erik already offered a nice solution, but I wanted to comment on why
it [OP's function + apply] did not work."

Josh

On Mon, Jul 19, 2010 at 1:03 PM, Joshua Wiley <jwiley.psych at gmail.com> wrote:
> Jason,
>
> Erik already offered a nice solution, but I wanted to comment on why
> it did not work.  apply() works on arrays and, of course, matrices.
> When you pass a data frame to apply, it will try to coerce it to a
> matrix.  Matrices only contain a single class of data (unlike data
> frames which can have separate classes for each column).  The
> hierarchy is logical < integer < real < complex < character.  Since
> a10 is character, everything is converted up to character.  This
> causes sum() to fail because it is passed character data.  This also
> explain why doit() works if you pass the data frame rows to it
> directly  doit(myDF[1 ,]) .
>
> You can find all this in the documentation for ?apply and ?as.matrix
>
> Cheers,
>
> Josh
>
> On Mon, Jul 19, 2010 at 12:36 PM, jd6688 <jdsignature at gmail.com> wrote:
>>
>>>myDF =
>> data.frame(id=c("A10","A20"),d1=c(.3,.3),d2=c(.4,.4),d3=c(-.2,.5),d4=c(-.3,.6),d5=c(.5,-.2),d6=c(.6,-.4),d7=c(-.9,-.5),d8=c(-.8,-.6))
>>
>>>doit=function(x)c(x[1],sum_LK_positive=sum(x[-1][x[-1]>0]),sum_LK_negative=sum(x[-1][x[-1]<0]))
>>
>>> myDF
>>   id  d1  d2   d3   d4   d5   d6   d7   d8
>> 1 A10 0.3 0.4 -0.2 -0.3  0.5  0.6 -0.9 -0.8
>> 2 A20 0.3 0.4  0.5  0.6 -0.2 -0.4 -0.5 -0.6
>>>  t(apply(myDF,1,doit))
>>
>>
>> Error in sum(x[-1][x[-1] > 0]) : invalid 'type' (character) of argument:
>>
>> I changed the id=c(100,101) in myDF, it worked. are there any way to have
>> this working if the id=c("a10","a20")?
>>
>> Thanks,
>>
>> --
>> View this message in context: http://r.789695.n4.nabble.com/invalid-type-error-tp2294491p2294491.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>>
>
>
>
> --
> Joshua Wiley
> Ph.D. Student, Health Psychology
> University of California, Los Angeles
> http://www.joshuawiley.com/
>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/