[R] Help needed on applying a function across different data sets and aggregating the results into a single data set

[David Winsemius]

On Jan 1, 2010, at 10:34 PM, Girish A.R. wrote:

>
> Hi folks,
>
> Wish y'all a Happy New Year 2010!
>
> I need some help with the following:
>
> Say I have lots of data sets, on which I have to apply a certain  
> function on
> the same set of columns in each of the data set. Let's take, for ex,  
> the
> typical data set is:
>
> df1 <- as.data.frame(cbind(rnorm(10),rnorm(10)))
> names(df1)[1] <- "A"
> names(df1)[2] <- "B"
>
> There are many such data sets, df2,df3,... I have the names stored  
> in a list
> DF <- cbind("df1","df2",...,"df100")

Unfortunately, that is not a list, but rather a character vector
 > DF <- cbind("df1","df2","df100")
 > str(DF)
  chr [1, 1:3] "df1" "df2" "df100"

Instead define it as a list of objects (i.e., with no quotes):

LL <- list(df1, df2, .... , df100)
#and then
lapply(LL, function(x) lsfit(x$A,x$B) )

-- 
Daid.

>
> I now need to apply the following function:
> a <- lsfit(df1$A,df1$B)
>
> and stack up the following results:
> a$coef
> Intercept          X
> -0.1479750  0.2485416
>
> So, I would end up with as many rows as there are data sets.
>
> I think sapply would be the function I should be looking for (at  
> least I
> have used it in the case of applying a function across different  
> columns of
> the same data set), but for some reason I'm not able to nail down  
> the final
> stages in this case.
>
> Earlier, I used something like the following in the case of applying a
> function across all columns(except the first) of the same data set:
> my.func <- function(x){
> mod <- lrm(my.data$y ~ x)
> data.frame(t(anova(mod)[1, ]), R2 = mod$stats[10])
>
> sapply(my.data[,-1],my.func)
>
> Where I need help is how to pass the reference of the names of the  
> different
> data sets to the sapply funtion.
>
> Thanks!
> -Girish
>
> ====================================
> sessionInfo()
> R version 2.10.0 (2009-10-26)
> i386-pc-mingw32
>
> locale:
> [1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United
> States.1252
> [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C
> [5] LC_TIME=English_United States.1252
>
> attached base packages:
> [1] grid      stats     graphics  grDevices utils     datasets   
> methods
> base
>
> other attached packages:
> [1] lattice_0.17-26 RWinEdt_1.8-2   ggplot2_0.8.5   digest_0.4.2
> reshape_0.8.3
> [6] plyr_0.1.9      proto_0.3-8
>
> loaded via a namespace (and not attached):
> [1] Formula_0.2-0    kinship_1.1.0-23 MASS_7.3-4       nlme_3.1-96
> plm_1.2-1
> [6] sandwich_2.2-4   splines_2.10.0   survival_2.35-8  tools_2.10.0
>
> -- 
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> Sent from the R help mailing list archive at Nabble.com.
>
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