[R] Merge or combine data frames with missing columns

[Charles C. Berry]

On Mon, 29 Dec 2008, Mark Heckmann wrote:

>
> Hi R-experts,
>
> suppose I have a list with containing data frame elements:
>
> [[1]]
> (Intercept)          y1          y2          y3          y4
> -6.64              0.761      0.383      0.775      0.163
>
> [[2]]
> (Intercept)          y2          y3
> -3.858             0.854      0.834
>
> Now I want to put them into ONE dataframe like this:
>               (Intercept)           y1          y2         y3           y4
>   1           -6.64              0.761      0.383      0.775      0.163
>   2         -3.858                  NA       0.854      0.834        NA
>
> The problem I encounter is that not always all possible columns (Intercept,  y1,  y2, y3,  y4) exist or at least have NA entries .
>
> I cannot figure out how (e.g. with merge)...

Just use a nested for loop:

> my.list <- list(c(a=1,b=2,c=3),c(a=10,b=20),c(g=7,h=8))
> dat <- data.frame()
> for(i in seq(along=my.list)) for(j in names(my.list[[i]])) dat[i,j] <- my.list[[i]][j]


If what you actually wanted was a _matrix_, and if it is rather large, 
faster solutions might be possible using tapply or sapply.

HTH,

Chuck


>
> TIA, Mark
>
>
> -- 
> Mark Heckmann (Dipl. Wirt.-Ing.)
> phone +49 (0) 421/1614618
>
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Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901