Rank a sorted dataset using apply function

Question

My dataframe looks like this:

head(temp$HName)

[1] "UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT TYLER"
[2] "METHODIST HOSPITAL,THE"                            
[3] "TOMBALL REGIONAL MEDICAL CENTER"                   
[4] "METHODIST SUGAR LAND HOSPITAL"                     
[5] "GULF COAST MEDICAL CENTER"                         
[6] "VHS HARLINGEN HOSPITAL COMPANY LLC"   

head(temp$Rate)

[1] 7.3 8.3 8.7 8.7 8.8 8.9
76 Levels: 7.3 8.3 8.7 8.8 8.9 9 9.1 9.2 9.3 9.4 9.5 9.6 ... 17.1

> head(temp$Rank)
[1] NA NA NA NA NA NA

The temp$Rate is sorted. I am trying to write a function assignRank which gives me a new column temp$Rank which has values as 1, 2, 3, 3, 4, 5

My code is as below:

tapply(temp$Rank,temp$Rate, assignRank)

where :

    assignRank<- function(r=1){
      temp$Rank <- r
      r <- r + 1
      return(r)
    }

I get following error when running tapply

   tapply(temp$Rank,temp$Rate, assignRank)
 Show Traceback

 Rerun with Debug
 Error in `$<-.data.frame`(`*tmp*`, "Rank", value = c(NA, NA)) : 
  replacement has 2 rows, data has 301

Please advise where I am going wrong?

hi Roland!. rank function has three ways to tackle ties which is first, random and average. In case i use "first" or "random" the rank as i understand from documentation will give the rank of 3rd and 4th row of my data set as 3,4. If I use average it will average out this two values. I want to preserve the rank of tied element which in my example is 3,3. — Ravi Shankar Hela, Sep 12 '14 at 08:49

David Arenburg · Accepted Answer · 2014-09-12T09:43:26.710

I use data.table for stuff like this, because both sorting and ranking are very efficient/simple syntax

library(data.table)
setkey(setDT(temp), Rate) # This will sort your data set by Rate in case it's not yet sorted
temp[, Rank := .GRP, by = Rate]
temp
#                                                 HName Rate Rank
# 1: UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT TYLER  7.3    1
# 2:                             METHODIST HOSPITAL,THE  8.3    2
# 3:                    TOMBALL REGIONAL MEDICAL CENTER  8.7    3
# 4:                      METHODIST SUGAR LAND HOSPITAL  8.7    3
# 5:                          GULF COAST MEDICAL CENTER  8.8    4
# 6:                 VHS HARLINGEN HOSPITAL COMPANY LLC  8.9    5

Or you could easily do the same using base R (assuming your data is sorted by Rank) just do

as.numeric(factor(temp$Rate))
## [1] 1 2 3 3 4 5

Or could also use dense_rank function from dplyr package (which will not require sorting the data set)

library(dplyr)
temp %>% 
  mutate(Rank = dense_rank(Rate))
#                                                HName Rate Rank
# 1 UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT TYLER  7.3    1
# 2                             METHODIST HOSPITAL,THE  8.3    2
# 3                    TOMBALL REGIONAL MEDICAL CENTER  8.7    3
# 4                      METHODIST SUGAR LAND HOSPITAL  8.7    3
# 5                          GULF COAST MEDICAL CENTER  8.8    4
# 6                 VHS HARLINGEN HOSPITAL COMPANY LLC  8.9    5

score 0 · Answer 2 · answered Sep 12 '14 at 10:52

0

Other options (if the data is ordered)

with(temp, cumsum(ave(Rate, Rate, FUN=function(x) c(1,x[-1]!=x[-length(x)]))))
#[1] 1 2 3 3 4 5



 with(temp, match(Rate, unique(Rate)) )
#[1] 1 2 3 3 4 5

answered Sep 12 '14 at 10:52

akrun

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Rank a sorted dataset using apply function

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