[R] Adding a new variable to each element of a list

Mon Nov 26 03:09:20 CET 2012

HI Steve,

You could try this:
ylist<-lapply(y,function(x) x)
 res<-lapply(mapply(c,result,Thing=ylist,SIMPLIFY=FALSE),function(x) do.call(cbind,x))
 res
#$`Error: subject`
 #         Df Sum Sq Mean Sq F value Pr(>F) Thing
#Residuals  4   12.4     3.1      NA     NA   0.5

#$`Error: subject:myfactor`
 #         Df   Sum Sq  Mean Sq  F value      Pr(>F)     Thing
#myfactor   2 14.93333 7.466667 13.57576 0.002682772 0.7724138
#Residuals  8  4.40000 0.550000       NA          NA 0.7724138

#But, it removes the "*", which BTW gets removed by individually inserting as you showed. 

A.K.

________________________________
From: Stephen Politzer-Ahles <politzerahless at gmail.com>
To: arun <smartpink111 at yahoo.com> 
Cc: R help <r-help at r-project.org> 
Sent: Sunday, November 25, 2012 8:35 PM
Subject: Re: [R] Adding a new variable to each element of a list

Hi Arun,

Thanks a lot for the help. I think I didn't make my request clear, though; sorry about that. What your example does is applies the values of y to each element in the list "result". However, what I'm actually trying to do is apply the nth element of y to the nth element of result. In other words, I'm trying to find a way in one command to do the equivalent of the following:

result[[1]][[1]]$Thing <- y[1]
result[[2]][[1]]$Thing <- y[2]
...etc.

Is this even possible? (Granted, for my purpose "result" is not a very long list, so it would not be difficult to just do those commands one at a time or in a for loop. At this point I'm just curious to figure out a more straightforward way to do it just for the sake of trying to learn more about how R works!)

If it helps put things into context, in my example the list "result" is a summary of an aov object, and each element in the list is one of the ANOVA effects; y is a vector of the partial eta squareds I calculated corresponding to each effect, and I'm trying to figure out a way to add those into the "result" object so it shows up when my colleague looks at the summary.

Best,
Steve

On Sat, Nov 24, 2012 at 5:22 PM, arun <smartpink111 at yahoo.com> wrote:

HI,
>
>The example data you gave have only one row for the 1st element of list.  So, it would be better to add it as:
> lapply(result,function(x) {x[[2]]<-y
> return(x)})
>#$`Error: subject`
>#Component 1 :
> #         Df Sum Sq Mean Sq F value Pr(>F)
>#Residuals  4   12.4     3.1              
>#
>#Component 2 :
>#[1] 0.5000000 0.7724138
>-----------------------------
>You can also do:
> lapply(result,function(x) {x[[1]][6]<-y[1]
> x[[1]][7]<-y[2]
> return(x)})
>#$`Error: subject`
> #         Df Sum Sq Mean Sq F value Pr(>F)  V6     V7
>#Residuals  4   12.4     3.1                0.5 0.7724
>
>#$`Error: subject:myfactor`
> #         Df Sum Sq Mean Sq F value   Pr(>F)  V6     V7
>#myfactor   2  14.93   7.467   13.58 0.002683 0.5 0.7724
>#Residuals  8   4.40   0.550                  0.5 0.7724    #Here it got repeated
>
>May be there are better methods
>
>A.K.
>
>
>
>
>
>
>----- Original Message -----
>From: Stephen Politzer-Ahles <politzerahless at gmail.com>
>To: r-help at r-project.org
>Cc:
>Sent: Saturday, November 24, 2012 5:33 PM
>Subject: [R] Adding a new variable to each element of a list
>
>Hello,
>
>I have a list of data with multiple elements, and each element in the list
>has multiple variables in it. Here's an example:
>
>### Make the fake data
>dv <- c(1,3,4,2,2,3,2,5,6,3,4,4,3,5,6)
>subject <- factor(c("s1","s1","s1","s2","s2","s2","s3","s3","s3",
>"s4","s4","s4","s5","s5","s5"))
>myfactor <- factor(c("f1","f2","f3","f1","f2","f3","f1","f2","f3",
>"f1","f2","f3","f1","f2","f3"))
>mydata <- data.frame(dv, subject, myfactor)
>
>### Do the anova and store the summary in "result"
>mydata.aov <- aov( dv ~ myfactor + Error(subject/myfactor), mydata )
>( result <- summary( mydata.aov ) ) # see the anova
>
>str(result)
>
>List of 2
>$ Error: subject         :List of 1
>  ..$ :Classes ‘anova’ and 'data.frame':        1 obs. of  5 variables:
>  .. ..$ Df     : num 4
>  .. ..$ Sum Sq : num 12.4
>  .. ..$ Mean Sq: num 3.1
>  .. ..$ F value: num NA
>  .. ..$ Pr(>F) : num NA
>  ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
>$ Error: subject:myfactor:List of 1
>  ..$ :Classes ‘anova’ and 'data.frame':        2 obs. of  5 variables:
>  .. ..$ Df     : num [1:2] 2 8
>  .. ..$ Sum Sq : num [1:2] 14.9 4.4
>  .. ..$ Mean Sq: num [1:2] 7.47 0.55
>  .. ..$ F value: num [1:2] 13.6 NA
>  .. ..$ Pr(>F) : num [1:2] 0.00268 NA
>  ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
>
>As you can see, each element in "result" has several variables (Df, Sum Sq,
>Mean Sq, F value, Pr(>F)):
>str( result[[2]][[1]] )
>Classes ‘anova’ and 'data.frame':       2 obs. of  5 variables:
>$ Df     : num  2 8
>$ Sum Sq : num  14.9 4.4
>$ Mean Sq: num  7.47 0.55
>$ F value: num  13.6 NA
>$ Pr(>F) : num  0.00268 NA
>
>Now I also have another vector of numbers that I would like to add to the
>list, as a 6th variable for each element:
>y <- c(.5, .7724138)
>
>Ideally, I would like each element in the list ("Error: subject" and
>"Error: subject:myfactor") to have a 6th variable, so the new str() would
>look like:
>List of 2
>$ Error: subject         :List of 1
>  ..$ :Classes ‘anova’ and 'data.frame':        1 obs. of  5 variables:
>  .. ..$ Df     : num 4
>  .. ..$ Sum Sq : num 12.4
>  .. ..$ Mean Sq: num 3.1
>  .. ..$ F value: num NA
>  .. ..$ Pr(>F) : num NA
>* .. ..$ Thing  : num 0.50*
>
>  ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
>$ Error: subject:myfactor:List of 1
>  ..$ :Classes ‘anova’ and 'data.frame':        2 obs. of  5 variables:
>  .. ..$ Df     : num [1:2] 2 8
>  .. ..$ Sum Sq : num [1:2] 14.9 4.4
>  .. ..$ Mean Sq: num [1:2] 7.47 0.55
>  .. ..$ F value: num [1:2] 13.6 NA
>  .. ..$ Pr(>F) : num [1:2] 0.00268 NA
>  *.. ..$ Thing  : num **0.772413*
>
>  ..- attr(*, "class")= chr [1:2] "summary.aov" "listof"
>
>Now, I know how to do this if I want to just add the variable to one
>element at a time:
>result[[1]][[1]]$Thing <- 0.5
>
>But I can't figure out how to do it for every element at once (other than
>using a for loop). I am able to index an existing variable from each
>element of a list (using lapply or sapply, based on the examples from
>http://stackoverflow.com/questions/1355355/how-to-avoid-a-loop-in-r-selecting-items-from-a-listand
>http://tolstoy.newcastle.edu.au/R/help/05/05/4678.html), but I can't figure
>out how to *set* a new variable for each element in a list. Does anyone
>
>know how to do this?
>
>Thank you,
>Steve Polizer-Ahles
>
>--
>Stephen Politzer-Ahles
>University of Kansas
>Linguistics Department
>http://people.ku.edu/~sjpa/
>
>    [[alternative HTML version deleted]]
>
>
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>

-- 
Stephen Politzer-Ahles
University of Kansas
Linguistics Department
http://people.ku.edu/~sjpa/