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I have factors from 0 to 39. Here is how they are ordered now:
> levels(items$label)
[1] "0" "1" "10" "11" "12" "13" "14" "15" "16" "17" "18" "19"
[13] "2" "20" "21" "22" "23" "24" "25" "26" "27" "28" "29" "3"
[25] "30" "31" "32" "33" "34" "35" "36" "37" "38" "39" "4" "5"
[37] "6" "7" "8" "9"
How do I reorder them in numeric order, for display purposes? I don't want to change the meaning of the data frame.
UPDATE: How do I update the original data frame, items, with the sorted factor, labels? This should not change the data frame substantively; I just want the factors to come out in the correct order in subsequent operations.
842
One way to change the level order is to use factor() on the factor and specify the order directly. In this example, the function ordered() could be used instead of factor() . Another way to change the order is to use relevel() to make a particular level first in the list.
To sort a data frame in R, use the order( ) function. By default, sorting is ASCENDING. Prepend the sorting variable by a minus sign to indicate DESCENDING order.
Occasionally you may want to re-order the levels of some factor variable in R. Fortunately this is easy to do using the following syntax: factor_variable <- factor(factor_variable, levels=c('this', 'that', 'those', ...))
To sort a numerical factor column in an R data frame, we would need to column with as. character then as. numeric function and then order function will be used.
sorted_labels <- paste(sort(as.integer(levels(items$label))))
Gives:
[1] "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" "10" "11"
[13] "12" "13" "14" "15" "16" "17" "18" "19" "20" "21" "22" "23"
[25] "24" "25" "26" "27" "28" "29" "30" "31" "32" "33" "34" "35"
[37] "36" "37" "38" "39"
Or (as mentioned in https://stackoverflow.com/a/15665655/109618):
sorted_labels <- order(levels(items$label)) - 1
# order by itself is a 1-based vector
# using `- 1` gives a 0-based vector
Per the updated question, this updates the data frame:
items$label <- factor(items$label, levels = sorted_labels)
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