[R] How to merge two functions into one?

[Rui Barradas]

Hello,

Instead of try(cor.test) you could try(return_cor).
Also, isn't there a bug in return_cor? See the commented line below.

return_cor = function(x, y, tresh = 0.05)  {
         z = cor.test(x,y)
         if(z[[3]] < tresh) {
       	  return(z[[4]])  # not z[[5]], always zero
           } else {
	        return(NA)
         }
}
cor_withN <- function(...) {
           res <- try(return_cor(...), silent=TRUE)
           ifelse(class(res)=="try-error", NA, res)
}

cor_withN(1:10, 1:10 + rnorm(10))
cor_withN(1:2, 1:2 + rnorm(2))


Hope this helps,

Rui Barradas


Em 22-02-2013 15:04, Jonsson escreveu:
> I am using the code below to calculate the correlation map between two
> datasets. This code worked fine.
>
>      dir1 <- list.files("D:thly", "*.bin", full.names = TRUE)
>      dir2 <- list.files("D:002", "*.envi", full.names = TRUE)
>      file_tot <- array(dim = c(1440, 720, 11, 2))
>      for(i in 1:length(dir1)) {
>          file_tot[, , i, 1] <- readBin(dir1[i], numeric(), size = 4,
>                                          n = 1440 * 720, signed = T)
>          file_tot[, , i, 2] <- readBin(dir2[i], numeric(), size = 4,
>                                          n = 1440 * 720, signed = T)
>      }
>      resultscor<-apply(file_tot,c(1,2),function(x){cor(x[,1],x[,2],use =
> "na.or.complete")})
>
> I would like to calculate the correlation only when the `P-value is lower
> than 0.05`. so this function bellow will do the job:
>
>       return_cor = function(x, y)  {
>          z = cor.test(x,y)
>          if(z[[3]] < 0.05) {
>          return(z[[5]])
>            } else {
>          return(NA)
>          }
>          }
>
> However I got this error(as some pairs of my data are less then 3):
>
>                   Error in cor.test.default(x, y) : not enough finite
> observations
>
> in order to avoid this error and return NA when there are less than 3
> pairs,this function does the job:
>
>            cor_withN <- function(...) {
>            res <- try(cor.test(...)$estimate, silent=TRUE)
>            ifelse(class(res)=="try-error", NA, res)
>             }
> Both functions worked perfectly.How can we merge both functions into one
> function so we calculate correlation when P value is (certain value,
> threshold) and also do the calculations even if there are less than 3 pairs.
>
>
>
>
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