[R] sorting a data.frame (df) by a vector (which is not contained in the df) - unexpected behaviour of match and factor

[drflxms]

Jeff,

thanks a lot for your quick reply and the hint!

Meanwhile I found a solution that works - at least for my case ;)
The code to get the job done is

df[order(match(df$level,desiredOrder)),]

So we seem in need of one order statement more. I found this solution
doing it stepwise:

## sorting the levels of the level column in the data.frame
df$level <- factor(df$level,levels=desiredOrder)
## sorting the data frame by the newly sorted level column
df[order(df$level),]

Maybe this solution is of a help for someone else as well?

But honestly I still do not exactly understand why
df[match(df$level,desiredOrder),] doesn't work...

Cheers, Felix

Am 29.12.11 10:58, schrieb Jeff Newmiller:
> Your desiredOrder vector is a vector of strings. Convert it to numeric and it should work.
> ---------------------------------------------------------------------------
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> Sent from my phone. Please excuse my brevity.
> 
> drflxms <drflxms at googlemail.com> wrote:
> 
>> Dear R colleagues,
>>
>> consider my data.frame named "df" with 3 columns - being level,
>> prevalence and sensitivity - and 7 rows of data (see dump below).
>>
>> df <-
>> structure(list(level = structure(1:7, .Label = c("0", "1", "10",
>> "100", "1010", "11", "110"), class = "factor"), prevalence =
>> structure(c(4L,
>> 2L, 3L, 5L, 6L, 1L, 7L), .Label = c("0.488", "0.5", "0.754",
>> "0.788", "0.803", "0.887", "0.905"), class = "factor"), sensitivity =
>> structure(c(6L,
>> 1L, 5L, 4L, 3L, 2L, 1L), .Label = c("0", "0.05", "0.091", "0.123",
>> "0.327", "0.933"), class = "factor")), .Names = c("level",
>> "prevalence",
>> "sensitivity"), class = "data.frame", row.names = c(NA, -7L))
>>
>> I'd like to order df by a vector which is NOT contained in the
>> data.frame. Let's call this vector desiredOrder (see dump below).
>>
>> desiredOrder <- c("0", "1", "10", "100", "11", "110", "1010")
>>
>> So after sorting, the order of the level column (df$level) should be in
>> the order of the vector desiredOrder (as well a the associated data in
>> the other columns).
>> I know that this is not an easy task to achieve by order(...) as the
>> order of desiredOrder isn't a natural one. But I would expect both of
>> the following to work:
>>
>> ## using match
>> df[match(df$level,desiredOrder),]
>>
>> ## using factor
>> df[factor(df$level,levels=desiredOrder),]
>>
>> Unfortunately the result isn't what I expected: I get a data.frame with
>> the level column in the order 0,1,10,100,110,1010,11 instead of the
>> order in desiredOrder (0,1,10,100,11,110,1010).
>>
>> Does anybody see, what I am doing wrong?
>> I'd appreciate any kind of help very much!
>> Best regards, Felix
>>
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