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Sorting has been discussed quite a bit here, but I have a particular problem. I have a data frame (df) with several columns. All the observations belong to one of three types, say C1, C2, and C3. Of the various columns, one contains a value which I will call frequency (f). Example df: 

 Type freq Val C3. 0.34. 10-A C1. 0.90. 4-A C2. 0.40. 5-B C1. 0.65. 3-C C2. 0.77. 5-D C3. 0.11. 5-D

I need to sort this table so that the primary key is the Type, and secondary key is the frequency. However, and here’s my problem, they need to be sorted by a particular order of type. I need them by C1, C3, C2. So the final table looks like this:

 Type freq Val C1. 0.90. 4-A C1. 0.65. 3-C C3. 0.34. 10-A C3. 0.11. 5-D C2. 0.77. 5-D C2. 0.40. 5-B

Is there a way to do this? To pick the particular ordering scheme of the column Type. Any suggestion is much appreciated. Thanks

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1 Answer 1

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We can convert the 'Type' to factor with levels specified in the custom order

library(dplyr) df1 %>% arrange(factor(Type, levels = c('C1.', 'C3.', 'C2.')), desc(freq)) # Type freq Val #1 C1. 0.90. 4-A #2 C1. 0.65. 3-C #3 C3. 0.34. 10-A #4 C3. 0.11. 5-D #5 C2. 0.77. 5-D #6 C2. 0.40. 5-B

Or using data.table

library(data.table) setDT(df1)[, Type := factor(Type, levels = c('C1.', 'C3.', 'C2.'))] setorder(df1, Type, -freq)

In base R, we can do

df1[order(factor(df1$Type, levels = c('C1.', 'C3.', 'C2.')), -df1$freq),]

data

df1 <- structure(list(Type = c("C3.", "C1.", "C2.", "C1.", "C2.", "C3." ), freq = c("0.34.", "0.90.", "0.40.", "0.65.", "0.77.", "0.11." ), Val = c("10-A", "4-A", "5-B", "3-C", "5-D", "5-D")), class = "data.frame", row.names = c(NA, -6L))
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3 Comments

I’m working with the “dplyr” library. My final df is arranging freq correctly, but the order of the Type is yielding C1, C2, C3, and not C1, C3, C2. I wonder if there’s something missing.
@Orion11 If you neeed to change the column, assign the factor output to that column and then it should work
Ok. I got it to work. I was missing the "$Type" part. Thank you very much.

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