[R] Interdependencies of variable types, logical expressions and NA
PIKAL Petr
petr.pikal at precheza.cz
Thu Apr 28 09:41:32 CEST 2016
Hi
Your script is not reproducible.
Creating Check_U_0__Kd_1_2011 from Umsatz_2011 and Kunde01_2011
Error in ifelse(Kunden01[[Umsatz]] == 0 & Kunden01[[Kunde]] == 1, 1, 0) :
object 'Kunden01' not found
>
This is interesting
x <- c(NA, FALSE, TRUE)
names(x) <- as.character(x)
outer(x, x, "&") ## AND table
<NA> FALSE TRUE
<NA> NA FALSE NA
FALSE FALSE FALSE FALSE
TRUE NA FALSE TRUE
>
I am not sure, but the logic for AND is to return TRUE only when both expressions are TRUE.
so
T&T = T
F&F = F
T&NA = NA (you cannot decide hence NA)
F&NA = F (you can decide that regardless of NA the result must be F)
outer(x, x, "|") ## OR table
<NA> FALSE TRUE
<NA> NA NA TRUE
FALSE NA FALSE TRUE
TRUE TRUE TRUE TRUE
OTOH the logic for OR table is that if one of the expressions is TRUE the result must be TRUE
T | T = T
F | F = F
T&NA = T (you can decide that regardless value in NA the result must be T)
F&NA = NA (you cannot decide hence NA)
And I believe that all your results can be explained by this logic.
Cheers
Petr
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
> G.Maubach at weinwolf.de
> Sent: Thursday, April 28, 2016 9:08 AM
> To: r-help at r-project.org
> Subject: [R] Interdependencies of variable types, logical expressions and NA
>
> Hi All,
>
> my script tries to do the following on factors:
>
> > ## Check for case 3: Umsatz = 0 & Kunde = 1
> > for (year in 2011:2015) {
> + Umsatz <- paste0("Umsatz_", year)
> + Kunde <- paste0("Kunde01_", year)
> + Check <- paste0("Check_U_0__Kd_1_", year)
> +
> + cat('Creating', Check, 'from', Umsatz, "and", Kunde, '\n')
> +
> + Kunden01[[ Check ]] <- ifelse(Kunden01[[ Umsatz ]] == 0 &
> + Kunden01[[ Kunde ]] == 1,
> + 1, 0
> + )
> + Kunden01[[ Check ]] <- factor(Kunden01[[ Check ]],
> + levels=c(1, 0),
> + labels= c("Check 0", "OK")
> + )
> +
> + }
> Creating Check_U_0__Kd_1_2011 from Umsatz_2011 and Kunde01_2011
> Creating Check_U_0__Kd_1_2012 from Umsatz_2012 and Kunde01_2012
> Creating Check_U_0__Kd_1_2013 from Umsatz_2013 and Kunde01_2013
> Creating Check_U_0__Kd_1_2014 from Umsatz_2014 and Kunde01_2014
> Creating Check_U_0__Kd_1_2015 from Umsatz_2015 and Kunde01_2015
> >
> > table(Kunden01$Check_U_0__Kd_1_2011, useNA = "ifany")
>
> Check 0 OK <NA>
> 1 16 13
> > table(Kunden01$Check_U_0__Kd_1_2012, useNA = "ifany")
>
> Check 0 OK <NA>
> 1 17 12
> > table(Kunden01$Check_U_0__Kd_1_2013, useNA = "ifany")
>
> Check 0 OK <NA>
> 2 17 13
> > table(Kunden01$Check_U_0__Kd_1_2014, useNA = "ifany")
>
> Check 0 OK <NA>
> 1 15 14
> > table(Kunden01$Check_U_0__Kd_1_2015, useNA = "ifany")
>
> Check 0 OK <NA>
> 2 15 13
> >
> > Kunden01$Check_U_0__Kd_1_all <-
> ifelse(Kunden01$Check_U_0__Kd_1_2011 ==
> 1 |
> + Kunden01$Check_U_0__Kd_1_2012 ==
> 1 |
> + Kunden01$Check_U_0__Kd_1_2013 ==
> 1 |
> + Kunden01$Check_U_0__Kd_1_2014 ==
> 1 |
> + Kunden01$Check_U_0__Kd_1_2015 ==
> 1,
> + 1, 0)
> >
> > table(Kunden01$Check_U_0__Kd_1_all, useNA = "ifany")
>
> 0 <NA>
> 7 23
>
> (Ann.: I made the values up. But the relations equal real world data.)
>
> I had expected to get back a factor or at least a numeric variable
> containing 0, 1 and NA, instead 1 is not included.
>
> I searched the web for information on the treatment of logical expressions
> when the data contains NA. I found:
>
> 1.
> https://stat.ethz.ch/R-manual/R-devel/library/base/html/NA.html
> Examples
> # Some logical operations do not return NA
> c(TRUE, FALSE) & NA
> c(TRUE, FALSE) | NA
>
> 2.
> https://stat.ethz.ch/R-manual/R-devel/library/base/html/Logic.html
> NA is a valid logical object. Where a component of x or y is NA, the
> result will be NA if the outcome is ambiguous. In other words NA & TRUE
> evaluates to NA, but NA & FALSE evaluates to FALSE. See the examples
> below.
>
> ## construct truth tables :
> x <- c(NA, FALSE, TRUE)
> names(x) <- as.character(x)
> outer(x, x, "&") ## AND table
> outer(x, x, "|") ## OR table
> Ann. Not very useful. How should it be read?
>
> 3.
> http://www.ats.ucla.edu/stat/r/faq/missing.htm
> Good explanation for NA in general and in analysis, but no information
> about NA in logical expressions.
>
> Then I made some tests with different data types and variables with NA:
>
> -- cut --
>
> # 2016-04-27-001_truth_table_for_logicals_and_NA.R
>
> # Test 1
> var2 <- c(TRUE, FALSE)
> var3 <- c(NA, NA)
> var1 <- c(1, 1)
> ds <- data.frame(var1, var2, var3)
> ds
>
> ds$value_and_logical <- ifelse(ds$var1 | ds$var2, TRUE, FALSE)
> ds$logical_and_na <- ifelse(ds$var2 | ds$var3, TRUE, FALSE)
> ds$value_and_na <- ifelse(ds$var1 | ds$var3, TRUE, FALSE)
>
> print(ds)
> # Output
> # var1 var2 var3 value_and_logical logical_and_na value_and_na
> # 1 1 TRUE NA TRUE TRUE TRUE
> # 2 1 FALSE NA TRUE NA TRUE
>
> # Test 2
> ds$var1 <- factor(ds$var1, levels = c(0, 1), labels = c("NOT ok", "OK"))
> ds$var2 <- factor(ds$var2, levels = c(0, 1), labels = c("NOT ok", "OK"))
> ds$var3 <- factor(ds$var3, levels = c(0, 1), labels = c("NOT ok", "OK"))
>
> ds$value_and_logical <- ifelse(ds$var1 | ds$var2, TRUE, FALSE)
> ds$logical_and_na <- ifelse(ds$var2 | ds$var3, TRUE, FALSE)
> ds$value_and_na <- ifelse(ds$var1 | ds$var3, TRUE, FALSE)
>
> # Output (abbrev.)
> # Warning message:
> # In Ops.factor(ds$var1, ds$var3) : ?|? ist nicht sinnvoll für Faktoren
>
> print(ds)
> # Output
> # var1 var2 var3 value_and_logical logical_and_na value_and_na
> # 1 OK <NA> <NA> NA NA NA
> # 2 OK <NA> <NA> NA NA NA
>
> -- cut --
>
> I had expected to get the same result in Test 2 as in Test 1.
>
> Where can I find information and documentation about NA handling in
> logical expressions on different variable types?
>
> Kind regards
>
> Georg
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> and provide commented, minimal, self-contained, reproducible code.
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