[R] result numeric(0) when using variable1[which(variable2="max(variable2)"]

Duncan Murdoch murdoch.duncan at gmail.com
Tue Jan 17 15:22:59 CET 2012

On 17/01/2012 5:35 AM, Nerak wrote:
> Dear all,
> I have a question about the knowing for which row I have the max value of
> one of my variables.
> I calculated the Rsquared for different columns and made a list to gather
> them. I unlisted this list to create a vector with this values. I want to
> know for which column I have the max value of Rsquared.
> The columns were always named in the same way. They always start with
> results4$depth_ following by the number. The numbers are constructed as:
> seq(1,10,0.1). But if the R squared values are now in 1 column, I don’t know
> for which column they are calculated. So I made a new data frame with both
> columns:
> R2<- unlist(LIST)
> Cvalue<- c(seq(1,10,0.1))
> results5<- data.frame(Cvalue,R2)
> # I know I can calculate the max value of Rsquared by this way:
> max(results5$R2)
> # now I want to know to which Cvalue this belongs. I would write it like
> this:
> results5$Cvalue[which(results5$R2 == "max(results5$R2)")]

Don't use quotes on the expression.  None of your R2 values are the string


which is why you're getting numeric(0).

You can also make it simpler by using the which.max() function.

Duncan Murdoch

> # But I always get the solution:
> numeric(0)
> # I don’t know if these Rsquared values are in a kind of format that this
> doesn’t work? (I used before for similar things, and I experienced that for
> example it cannot works if R recognizes the values as a date).  Maybe
> because it’s with a lot of decimals? (eg 2.907530e-01) I know that
> max(results5$R2) is in this example 0.6081547 and I can see that that
> belongs to the Cvalue == 1.8. It works in the opposite way.
> results5$R2[which(results5$Cvalue == "1.8")]
> # But neither
> results5$Cvalue[which(results5$R2 == "0.6081547")]
> # nor
> results5$Cvalue[which(results5$R2 == "max(results5$R2)")]
> # works…
> I hope someone can help me with this problem
> Kind regards
> Nerak
> --
> View this message in context: http://r.789695.n4.nabble.com/result-numeric-0-when-using-variable1-which-variable2-max-variable2-tp4302887p4302887.html
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