[R] looking for 'tied rows' in dataframe

[Evan Cooch]

Good suggestion, and for my purposes, will solve the problem. Thanks!

On 3/18/2019 12:37 PM, Ben Tupper wrote:
> Hi,
>
> Might you replaced 'T' with a numeric value that signals the TRUE case without rumpling your matrix?  0 might be a good choice as it is never an index for a 1-based indexing system.
>
> hold=apply(test,1,which.max)
> hold[apply(test,1,isUnique)==FALSE] <- 0
> hold
> [1] 1 2 0
>   
>
>
>> On Mar 17, 2019, at 8:17 PM, Evan Cooch <evan.cooch using gmail.com> wrote:
>>
>> Solved --
>>
>> hold=apply(test,1,which.max)
>>      hold[apply(test,1,isUnique)==FALSE] <- 'T'
>>
>> Now, all I need to do is figure out how to get <- 'T' from turning everything in the matrix to a string.
>>
>>
>> On 3/17/2019 8:00 PM, Evan Cooch wrote:
>>> Got relatively close - below:
>>>
>>> On 3/17/2019 7:39 PM, Evan Cooch wrote:
>>>> Suppose I have the following sort of structure:
>>>>
>>>> test <- matrix(c(2,1,1,2,2,2),3,2,byrow=T)
>>>>
>>>> What I need to be able to do is (i) find the maximum value for each row, (ii) find the column containing the max, but (iii) if the maximum value is a tie (in this case, all numbers of the row are the same value), then I want which.max (presumably, a tweaked version of what which.max does) to reurn a T for the row where all values are the same.
>>>>
>>>> Parts (i) and (ii) seem easy enough:
>>>>
>>>> apply(test,1,max)  --- gives me the maximum values
>>>> apply(test,1,which.max) --- gives me the column
>>>>
>>>> But, standard which.max doesn't handles ties/duplicates in a way that serves my need. It defaults to returning the first column containing the maximum value.
>>>>
>>>> What I'd like to end up with is, ultimately, something where apply(test,1,which.max) yields 1,2,T  (rather than 1,2,1).
>>>>
>>>> So, a function which does what which.max currently does if the elements of the row differ, but which returns a T (or some such) if in fact the row values are all the same.
>>>>
>>>> I've tried a bunch of things, to know avail. Closest I got was to use a function to test for whether or not a vector
>>>>
>>>> isUnique <- function(vector){
>>>>                   return(!any(duplicated(vector)))
>>>>              }
>>>>
>>>> which returns TRUE if values of vector all unique. So
>>>>
>>>> apply(test,1,isUnique)
>>>>
>>>> returns
>>>>
>>>> [1]  TRUE  TRUE FALSE
>>>>
>>>> but I'm stuck beyond this.
>>> The following gets me pretty close,
>>>
>>> test_new <- test
>>> test_new[which(apply(test,1,isUnique)==FALSE),] <- 'T'
>>>
>>> but is clunky.
>>>
>>>
>>>
>>>
>>>
>>>
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> Ben Tupper
> Bigelow Laboratory for Ocean Sciences
> 60 Bigelow Drive, P.O. Box 380
> East Boothbay, Maine 04544
> http://www.bigelow.org
>
> Ecological Forecasting: https://eco.bigelow.org/
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