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using if else function to complete a column in data frame

3 messages · Cacique Samurai, PIKAL Petr, David Winsemius

Original
Cacique Samurai
# 
Hello all!

I?m trying to complete the "movimento" column in dataframe based in
the values of "kmr" column in two sequential lines, as below:

data example (dput in the end of email):

         ID    kmr movimento
5    10.700 314.20        NA
1    10.700 278.74        NA
2    10.700 278.74        NA
3    10.700 278.74        NA
4    10.700 278.74        NA
494 100.700 269.94        NA
500 100.700 278.74        NA
499 100.700 314.20        NA
495 100.700 278.74        NA
498 100.700 278.74        NA
496 100.700 255.40        NA
497 100.700 255.10        NA

Once I have different IDs, I wrote this function:

move = function (x){

  for (j in x$ID){

    for (i in 2:length(x$kmr)-1){

      if (x$kmr[i+1]  < x$kmr[i]) {
        x$movimento[i+1] <- "jusante"
      } else if (x$kmr[i+1] > x$kmr[i]) {
        x$movimento[i+1] <- "montante"
      } else {
        x$movimento[i+1] <- "parado"
      }

    }

  }

  return (x)
}

Worked pretty well with just one ID, but with many IDs the function
didn?t detach different IDs.

         ID    kmr movimento
5    10.700 314.20      <NA>
1    10.700 278.74   jusante
2    10.700 278.74    parado
3    10.700 278.74    parado
4    10.700 278.74    parado
494 100.700 269.94   jusante <-- this should be <NA>
500 100.700 278.74  montante
499 100.700 314.20  montante
495 100.700 278.74   jusante
498 100.700 278.74    parado
496 100.700 255.40   jusante
497 100.700 255.10   jusante

I also tried remove the first If condition and pass this function
using lapply in the splitted original data-frame, but didn?t work as
well.

Some onde can help?

Thanks in advanced,

Raoni

structure(list(ID = c("10.700", "10.700", "10.700", "10.700",
"10.700", "100.700", "100.700", "100.700", "100.700", "100.700",
"100.700", "100.700"), kmr = c(314.2, 278.74, 278.74, 278.74,
278.74, 269.94, 278.74, 314.2, 278.74, 278.74, 255.4, 255.1),
    movimento = c(NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA,
    NA)), .Names = c("ID", "kmr", "movimento"), row.names = c(5L,
1L, 2L, 3L, 4L, 494L, 500L, 499L, 495L, 498L, 496L, 497L), class = "data.frame")
PIKAL Petr
# 
Hi

Split option seems to me the most effective and ifelse is in this case not necessary.

You can use this function to estimate levels

fff <- function(x) sign(diff(x))
test.s <- split(test, test$ID)
for (i in 1:length(test.s)) test.s[[i]]$movimento[-1] <- fff(test.s[[i]][,2])
test <- do.call(rbind, test.s)
test[,3] <- factor(test[,3], levels=c(-1, 0, 1), labels=c("jusante", "parado", "montante"))
test

To avoid extension of row names you can use
library (plyr)
test<-ldply (test.s, data.frame)

instead of do.call.

I tried assigning factor within for cycle

fff<- function(x) factor(sign(diff(x)), levels=c(-1, 0, 1), labels=c("jusante", "parado", "montante"))
test.s <- split(test, test$ID)
for (i in 1:length(test.s)) test.s[[i]]$movimento[-1] <- fff(test.s[[i]][,2])
test <- do.call(rbind, test.s)
test

but assigned in this case is not factor but numeric vector, which seems to me strange. Maybe somebody could explain this behaviour

Cheers
Petr
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David Winsemius
# 
The inner loop was not "recognizing" (or more accurately you were not causing the code to account for the fact) that you wanted this to be done within values of ID. Each pass of the outer loop was doing the same process inside the inner loop.
David Winsemius
Alameda, CA, USA