[R] How do I get rid of list elements where the value is NULL before applying rbind?

[jim holtman]

Here is a function I use to return the non-NULL elements of a list:

 delete.NULLs  <-  function (x.list)
{
    x.list[unlist(lapply(x.list, length) != 0)]
}


On Thu, Jul 22, 2010 at 2:22 PM, Ted Byers <r.ted.byers at gmail.com> wrote:
> Here is the function that makes the data.frames in the list:
>
> funweek <- function(df)
>  if (length(df$elapsed_time) > 5) {
>    res = fitdist(df$elapsed_time,"exp")
>    year = df$sale_year[1]
>    sample = df$sale_week[1]
>    mid = df$m_id[1]
>    estimate = res$estimate
>    sd = res$sd
>    samplesize = res$n
>    loglik = res$loglik
>    aic = res$aic
>    bic = res$bic
>    chisq = res$chisq
>    chisqpvalue = res$chisqpvalue
>    chisqdf = res$chisqdf
>    if (!is.null(estimate) && !is.null(sd) && !is.null(loglik) &&
> !is.null(aic) && !is.null(bic) &&
>        !is.null(chisq) && !is.null(chisqpvalue) && !is.null(chisqdf)) {
>      rv =
> data.frame(mid,year,sample,samplesize,estimate,sd,loglik,aic,bic,chisq,chisqpvalue,chisqdf)
>      rv
>    }
>  }
>
> I use the following, with different data, successfully:
>
> z <-
> lapply(split(moreinfo,list(moreinfo$m_id,moreinfo$sale_year,moreinfo$sale_week),drop
> = TRUE), funweek)
> qqq <- z[, c('mid', 'year', 'sample', 'samplesize', 'estimate', 'sd',
> 'loglik', 'aic','bic', 'chisq', 'chisqpvalue', 'chisqdf')]
> ndf2 <- do.call(rbind, qqq)
>
>
> However, I am now getting the following error:
>
>> qqq <- z[, c('mid', 'year', 'sample', 'samplesize', 'estimate', 'sd',
>> 'loglik', 'aic','bic', 'chisq', 'chisqpvalue', 'chisqdf')]
>> Error in z[, c("mid", "year", "sample", "samplesize", "estimate", "sd",  :
>>   incorrect number of dimensions
>>
>
>
> My suspicion is that it is due to the fact that sometimes one or more of the
> elements in my conditional block is null, so nothing is returned and that
> this puts a null element into z.  Here is a selection of a couple elements
> so you can see what is in 'z'.
>
> $`353.2010.0`
>>      mid year sample samplesize   estimate         sd   loglik      aic
>> rate 353 2010      0         17 0.06463837 0.01567335 -63.5621 129.1242
>>           bic    chisq chisqpvalue chisqdf
>> rate 129.9574 14.90239 0.001901994       3
>>
>> $`355.2010.0`
>> NULL
>>
>> $`376.2010.0`
>>      mid year sample samplesize   estimate         sd    loglik      aic
>> rate 376 2010      0          6 0.07228863 0.02950606 -21.76253 45.52506
>>           bic    chisq  chisqpvalue chisqdf
>> rate 45.31682 16.46848 4.946565e-05       1
>>
>
> You see the value for rowname = `355.2010.0` is NULL., and it is my guess
> that this leads to the error I show above.  But I can't confirm that yet,
> because I don't yet know how to get rid of rows that have a row name but
> only NULL as the value.
>
> I haven't seen this dealt with in the references I have read so far.
>
> I think I may be able to deal with it by creating dummy values for the
> fields the data frame requires, and then use SQL to remove them, but I'd
> rather not have to resort to that if I can avoid it.
>
> I can't believe there isn't something in the base package for R that would
> easily handle this, but not knowing the name of the function to look at, I
> haven't found it yet.
>
> Any information would be appreciated.
>
> Thanks
>
> Ted
>
>        [[alternative HTML version deleted]]
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?