CODEWITHSUNDEEP
rlistmean
Larusson
Larusson

Reputation: 267

mean of indexed elements across lists in R

I have a question similar to the problem raised in this question, however I am not interested in obtaining elementwise means within a list, but for each index value within an element across lists.

Give I have these three lists

ice_2000 = list(seq(1,5,1),seq(6,10,1),seq(11,15,1))
ice_1990 = list(seq(1,5,1),seq(6,10,1),seq(11,15,1))
ice_1980 = list(seq(1,5,1),seq(6,10,1),seq(11,15,1))

I want to find the mean sea ice across years per day per station...

x=c(1,2,3) ## years
y=c(1:5)   ## stations

...and store it in a new list with the same format as any of the three list above

Something like

[[day]][station]....[n station]
.
.
.
[[n day]][station]....[n station]

I have tried something like

average.ice =rep( list(rep(NA, length(y))), 3 ) 

foreach(x=x) %do% {
  foreach(y=y) %do% { 

    average.ice[[x]][y] = mean(c(ice_1980[[x]][y],ice_1990[[x]][y],ice_2000[[x]][y]))

  }
}

But I get NAs in my output

average.ice

[[1]]
[1] 1 2 3

[[2]]
[1] NA NA  8

[[3]]
[1] NA NA 13

Where am I going wrong? is there any smarter way within the apply family?

Upvotes: 1

Views: 94

Answers (2)

akuiper
akuiper

Reputation: 214927

You may be looking for something like this:

numOfStations <- length(ice_1980)

average.ice <- lapply(1:numOfStations, 
                      function(i) mapply(mean, ice_1980[[i]], ice_1990[[i]], ice_2000[[i]]))

Upvotes: 0

Robert
Robert

Reputation: 5152

Take much care with indexes. Is that what you want?

yy=c(1,2,3) ## years
st=c(1:5)   ## stations

average.ice =rep( list(rep(NA, length(st))), 3 ) 

library(foreach)

foreach(x=yy) %do% {
  foreach(y=st) %do% { 

    average.ice[[x]][y] = mean(c(ice_1980[[x]][y],ice_1990[[x]][y],ice_2000[[x]][y]))

  }
}

Upvotes: 1

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