Finding the average of R table object

user_9559530 0
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Other questions using "table" in their title are actually using data frame.

I want to keep this strictly about table object.

Suppose I have tables with same structure that I want to find the average of.

For example:

test1 <- head(table(iris$Sepal.Length, iris$Species))

(test1 + test1 + test1) / 3

> (test1 + test1 + test1) / 3
     
      setosa versicolor virginica
  4.3      1          0         0
  4.4      3          0         0
  4.5      1          0         0
  4.6      4          0         0
  4.7      2          0         0
  4.8      5          0         0

However, it cannot be done by:

> mean(c(test1,test1,test1))
[1] 0.8888889
> sum(c(test1,test1,test1)) / 3
[1] 16

Best approach I could find was to make the objects into a list of tables and use Reduce function:

Reduce(`+`, list(test1, test1, test1)) / 3

Is there more simpler way to do it without going back and forth using list object?

r average
1 Answers

We may loop over the array in the 1st two dimensions and get the mean

apply(replicate(3, test1), 1:2, mean, na.rm = TRUE)

-output

       setosa versicolor virginica
  4.3      1          0         0
  4.4      3          0         0
  4.5      1          0         0
  4.6      4          0         0
  4.7      2          0         0
  4.8      5          0         0

Or loop over a single dimension and get the rowMeans/colMeans

apply(replicate(3, test1), 2, rowMeans, na.rm = TRUE)
     
      setosa versicolor virginica
  4.3      1          0         0
  4.4      3          0         0
  4.5      1          0         0
  4.6      4          0         0
  4.7      2          0         0
  4.8      5          0         0

Both these methods are better than the Reduce approach with + especially when there are missing values as na.rm argument is found in both mean and rowMeans/colMeans

NOTE: replicate is used to create an array by replicating the object 'test1' n times.

If the object is already a list of tables, then convert to array with simplify2array before applying the apply

apply(simplify2array(list(test1, test1, test1)), 1:2, mean, na.rm = TRUE)
     
      setosa versicolor virginica
  4.3      1          0         0
  4.4      3          0         0
  4.5      1          0         0
  4.6      4          0         0
  4.7      2          0         0
  4.8      5          0         0
user_37322710
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