[R] dplyr's arrange function

[Daniel Nordlund]

On 6/15/2016 2:08 PM, Muhuri, Pradip (AHRQ/CFACT) wrote:
> Hello,
>
> I am using the dplyr's arrange() function to sort  one of the  many data frames  on a character variable (named "prevalence").
>
> Issue: I am not getting the desired output  (line 7 is the problem, which should be the very last line in the sorted data frame) because the sorted field is character, not numeric.
>
> The reproducible example and the output are appended below.
>
> Is there any work-around  to convert/treat  this character variable (named "prevalence" in the data frame below)  as numeric before using the arrange() function within the dplyr package?
>
> Any hints will be appreciated.
>
> Thanks,
>
> Pradip Muhuri
>
> # Reproducible Example
>
> library("readr")
> testdata <- read_csv(
> "indicator,  prevalence
> 1. Health check-up, 77.2 (1.19)
> 2. Blood cholesterol checked,  84.5 (1.14)
> 3. Recieved flu vaccine, 50.0 (1.33)
> 4. Blood pressure checked, 88.7 (0.88)
> 5. Aspirin use-problems, 11.7 (1.02)
> 6.Colonoscopy, 60.2 (1.41)
> 7. Sigmoidoscopy,  6.1 (0.61)
> 8. Blood stool test, 14.6 (1.00)
> 9.Mammogram,  72.6 (1.82)
> 10. Pap Smear test, 73.3 (2.37)")
>
> # Sort on the character variable in descending order
> arrange(testdata, desc(prevalence))
>
> # Results from Console
>
>                       indicator  prevalence
>                           (chr)       (chr)
> 1     4. Blood pressure checked 88.7 (0.88)
> 2  2. Blood cholesterol checked 84.5 (1.14)
> 3            1. Health check-up 77.2 (1.19)
> 4            10. Pap Smear test 73.3 (2.37)
> 5                   9.Mammogram 72.6 (1.82)
> 6                 6.Colonoscopy 60.2 (1.41)
> 7              7. Sigmoidoscopy  6.1 (0.61)
> 8       3. Recieved flu vaccine 50.0 (1.33)
> 9           8. Blood stool test 14.6 (1.00)
> 10      5. Aspirin use-problems 11.7 (1.02)
>
>
> Pradip K. Muhuri,  AHRQ/CFACT
>  5600 Fishers Lane # 7N142A, Rockville, MD 20857
> Tel: 301-427-1564
>
>
>

The problem is that you are sorting a character variable.

> testdata$prevalence
  [1] "77.2 (1.19)" "84.5 (1.14)" "50.0 (1.33)" "88.7 (0.88)" "11.7 (1.02)"
  [6] "60.2 (1.41)" "6.1 (0.61)"  "14.6 (1.00)" "72.6 (1.82)" "73.3 (2.37)"
>

Notice that the 7th element is "6.1 (0.61)".  The first CHARACTER is a 
"6", so it is going to sort BEFORE the "50.0 (1.33)" (in descending 
order).  If you want the character value of line 7 to sort last, it 
would need to be "06.1 (0.61)" or " 6.1 (0.61)" (notice the leading space).

Hope this is helpful,

Dan

Daniel Nordlund
Port Townsend, WA USA