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

[Girish A.R.]

Thanks for the replies, Jim, David, and Dennis (who replied to me directly)! 

To summarize, here's what worked for me:
===========
dflist <- list(df1, df2, df3)
lsfun <- function(df) with(df, lsfit(A, B)$coef)
res <- lapply(dflist, lsfun)
do.call(rbind, res)
===========

cheers,
-Girish


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")
> 
> 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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