question: ragged array

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if you set parameter simplify=TRUE, it returns a vector of the ragged
mean. In your case,

mean_rating <- tapply(ratok$value, ratok$project_id , mean,simplify = TRUE)

df<-data.frame(ID=dimnames(mean_rating)[[1]], mean=mean_rating)

Weidong Gu

On Sun, Oct 16, 2011 at 9:53 AM, Helene Schreyer
Hello,

I have a big problem which I?m just not able to solve.

I created the following mean value from the following dataset structure:

Id |value

1 ?| 2

1 ?| 3

1 ?| 4

2 ?| 2

2 ?| 1

3 ?| 5

4 ?| 3

etc.|etc.

with the command:

mean_rating <- tapply(ratok$value, ratok$project_id , mean,simplify = FALSE)

this gives me ?a ragged array:

mean_rating [1]
$`14` ###########==project_id

[1] 3.933333 #######==mean value

dim (mean_rating)
[1] 2214

I want to separate now the project_id from the mean value. So that I have
two separate ? ? ? ? columns (2 dimension).

How can I separate a ragged array into two variables?

*Additional information:*

I need this information to put the mean value into another dataset
(?projok?) at the correct project_id.

I would do that as follow:

k=projok[,1]

for(i in 1:2442) {

? ? ? ? ? ? ? ?projLineNb = which(mean_rating$project_id==k[i])

? ? ? ? ? ? ? ?projok$mean[i] = mean_rating$value[projLineNb]

}

But with a ragged array I can not refer to project_id. Or is there a
possibility that I can refer to the project_id in a ragged array?

mean_rating [[1]]
[1] 3.933333 ==I can refer to the value only

Thank you very much

Best,

Helene

? ? ? ?[[alternative HTML version deleted]]

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Hi:

Try this:

ratok <- data.frame(Id = rep(1:3, 3:1), value = c(2, 3, 4, 2, 1, 5))
aggregate(value ~ Id, data = ratok, FUN = mean)
  Id value
1  1   3.0
2  2   1.5
3  3   5.0

aggregate() returns a data frame with the Id variable and mean(value).

HTH,
Dennis

On Sun, Oct 16, 2011 at 6:53 AM, Helene Schreyer
Hello,