如何在R中找到每行的第一个和最后一个负值的列名

Question

I want to find the column name of first and last row with negative value and add it to the data frame as two columns as "firststatus" and "laststatus". Here is an example:

structure(c(NA, NA, "11", "-8.01e-14", NA, "6", NA, "-3", "-7", NA, 
        NA, NA, NA, "3", "-5.0015e-8", NA, NA, NA, NA, "-4.5e+00", NA, "50.5", "51", 
        "51", "50.5", "53", "52"), .Dim = c(3L, 9L), .Dimnames = list(
          c("1001", "1002", "1003"), c("50", "50.5", "51", "51.5", 
                                       "52", "52.5", "53", "firststatus", "laststatus")))

How can I make it? The output should be:

 dat$firststatus = c(50.5,51, 51)
dat$laststatus = c(50.5,53,52)

Thanks in advance for your advice.

Answer 1

You could do:

cbind(dat, `colnames<-`(t(apply(dat, 1, function(x) {
  x <- grep("-", x);
  colnames(dat)[x[c(1, length(x))]]
  })), c("firststatus", "laststatus")))
#>      50   50.5 51   51.5 52   52.5 53   firststatus laststatus
#> 1001 "9"  "-8" NA   NA   NA   NA   NA   "50.5"      "50.5"    
#> 1002 NA   NA   "-3" NA   "3"  NA   "-4" "51"        "53"      
#> 1003 "11" "6"  "-7" NA   "-5" NA   NA   "51"        "52"

^{Created on 2022-05-28 by the reprex package (v2.0.1)}