[datatable-help] Can you explain what is going on???

[Gerald Jean]

Hello,

the following code is extracted from a function where roughly 150 variables of a large data set are transformed using data.table.

The variable "membre" was coming out with one missing value, in trying to understand why, I extracted the code from the function, added a few "cat" statements and ran it directly in the terminal.

ttt.test.sima[, ":="  (membre = {##
+       cat(" Processing: membre", sep = "\n")
+       ttt <- membre
+       cat(paste(" Class ttt = ", class(ttt), sep = ""), sep = "\n")
+       cat(paste(" Length ttt = ", length(ttt), sep = ""), sep = "\n")
+       cat(paste(" sum(ttt == 0) = ", sum(ttt == "0"), sep = ""), sep = "\n")
+       ttt[ttt == "0"] <- "O"  ## A few capital "O" are coded as zero "0".
+       cat(paste(" sum(ttt == 0) = ", sum(ttt == "0"), sep = ""), sep = "\n")
+       ttt <- ifelse(PROV != " QC", " OAO",
+                     ifelse(membre == "", " Ma  ", membre))
+       cat(paste(" sum(ttt == 0) = ", sum(ttt == "0"), sep = ""), sep = "\n")
+       merge.levels(factor(ttt, levels = c("O", "N", " Ma  ", " OAO"),
+                           labels = c(" Oui", " Non", " Ma ", " OAO")),
+                    k = list(" Oui" = c(" Oui", " OAO")))})]
Processing: membre
Class ttt = character
Length ttt = 4750880
sum(ttt == 0) = 2
sum(ttt == 0) = 0
sum(ttt == 0) = 1

I don't understand why after the « ifelse» statement the temporary variable « ttt» is back with a single « 0 (zero)» in it, resulting of course in the missing value of the factor created from it.

Thanks for your support,

Gérald

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Gerald Jean, M. Sc. en statistiques
Conseiller senior en statistiques

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