[R] Trouble retrieving the second largest value from each row of a data.frame

[jim holtman]

try this:

> x <- read.table(textConnection("  value0 value60 value120 value180 value240 value300
+ 1  -13007  -11707   -11072   -12471   -12838   -13357
+ 2  -12838  -13210   -11176   -11799   -13210   -13845
+ 3  -12880  -11778   -11113   -12439   -13089   -13880
+ 4  -12805  -11653   -11071   -12385   -11561   -13317
+ 5  -12834  -13527   -11067   -11638   -13527   -13873
+ 6  -11068  -11698   -12430   -12430   -12430   -12814
+ 7  -12807  -14068   -11092   -11709   -11607   -13025
+ 8  -12770  -11665   -11061   -12373   -11426   -12805
+ 9  -12988  -11736   -11137   -12570   -13467   -13739
+ 10 -11779  -12873   -12973   -12537   -12973   -11146"), header=TRUE)
> closeAllConnections()
> # generate the indices of 1st&2nd largest in each row
> indx <- apply(x, 1, function(z){
+     order(z, decreasing=TRUE)[1:2]
+ })
> # now print out the data for each row
> for (i in seq(ncol(indx))){
+     cat('row:', i,
+         '1st:', x[i, indx[1,i]], 'col:', colnames(x)[indx[1,i]],
+         '2nd:', x[i, indx[2,i]], 'col:', colnames(x)[indx[2,i]], '\n')
+ }
row: 1 1st: -11072 col: value120 2nd: -11707 col: value60
row: 2 1st: -11176 col: value120 2nd: -11799 col: value180
row: 3 1st: -11113 col: value120 2nd: -11778 col: value60
row: 4 1st: -11071 col: value120 2nd: -11561 col: value240
row: 5 1st: -11067 col: value120 2nd: -11638 col: value180
row: 6 1st: -11068 col: value0 2nd: -11698 col: value60
row: 7 1st: -11092 col: value120 2nd: -11607 col: value240
row: 8 1st: -11061 col: value120 2nd: -11426 col: value240
row: 9 1st: -11137 col: value120 2nd: -11736 col: value60
row: 10 1st: -11146 col: value300 2nd: -11779 col: value0
>
>


On Fri, Jul 23, 2010 at 9:20 PM,  <mpward at illinois.edu> wrote:
> I have a data frame with a couple million lines and want to retrieve the largest and second largest values in each row, along with the label of the column these values are in. For example
>
> row 1
> strongest=-11072
> secondstrongest=-11707
> strongestantenna=value120
> secondstrongantenna=value60
>
> Below is the code I am using and a truncated data.frame.  Retrieving the largest value was easy, but I have been getting errors every way I have tried to retrieve the second largest value.  I have not even tried to retrieve the labels for the value yet.
>
> Any help would be appreciated
> Mike
>
>
>> data<-data.frame(value0,value60,value120,value180,value240,value300)
>> data
>   value0 value60 value120 value180 value240 value300
> 1  -13007  -11707   -11072   -12471   -12838   -13357
> 2  -12838  -13210   -11176   -11799   -13210   -13845
> 3  -12880  -11778   -11113   -12439   -13089   -13880
> 4  -12805  -11653   -11071   -12385   -11561   -13317
> 5  -12834  -13527   -11067   -11638   -13527   -13873
> 6  -11068  -11698   -12430   -12430   -12430   -12814
> 7  -12807  -14068   -11092   -11709   -11607   -13025
> 8  -12770  -11665   -11061   -12373   -11426   -12805
> 9  -12988  -11736   -11137   -12570   -13467   -13739
> 10 -11779  -12873   -12973   -12537   -12973   -11146
>> #largest value in the row
>> strongest<-apply(data,1,max)
>>
>>
>> #second largest value in the row
>> n<-function(data)(1/(min(1/(data[1,]-max(data[1,]))))+ (max(data[1,])))
>> secondstrongest<-apply(data,1,n)
> Error in data[1, ] : incorrect number of dimensions
>>
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?