[R] Creating New Variable Using Ifelse
Courtney Benjamin
cbenjami at BTBOCES.ORG
Thu Aug 10 14:43:25 CEST 2017
Thanks very much; with your tips, I was able to get the nested ifelse statement to work properly!
Courtney Benjamin
________________________________________
From: PIKAL Petr <petr.pikal at precheza.cz>
Sent: Thursday, August 10, 2017 5:39 AM
To: Courtney Benjamin; r-help at r-project.org
Subject: RE: Creating New Variable Using Ifelse
Hi
see in line
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Courtney
> Benjamin
> Sent: Thursday, August 10, 2017 5:55 AM
> To: r-help at r-project.org
> Subject: [R] Creating New Variable Using Ifelse
>
> Hello R Help List,
>
> I am an R novice and trying to use the ifelse function to create a new binary
> variable based off of the responses of two other binary variables; NAs are
> involved. I pulled it off almost successfully, but when I checked the counts of
> my new variable for accuracy, I found that a small portion of the NA cases were
> not being passed through as NAs, but as "0" counts in my new variable. My
> many attempts at creating a nested ifelse statement that would pass the NAs
> through properly have not been successful. Any help is greatly appreciated.
>
> Here is a MRE:?
>
> library(RCurl)
> data <-
> getURL("https://raw.githubusercontent.com/cbenjamin1821/careertech-
> ed/master/elsq2wbl.csv")
Did not work for me probably due to some restriction of data access.
> elsq2wbl <- read.csv(text = data)
>
> ##Recoding Negative Responses to NA
> elsq2wbl [elsq2wbl[, "EVERRELJOB"] < -3, "EVERRELJOB"] <- NA
> elsq2wbl [elsq2wbl[, "PSWBL"] < -2, "PSWBL"] <- NA
If you wanted recode values below zero to NA you can do this easily without any ifelse
> summary(test)
mp tepl kryst
Min. : 7.11 Min. :100.0 Min. : 21.70
1st Qu.:32.25 1st Qu.:400.0 1st Qu.: 24.15
Median :37.50 Median :500.0 Median : 26.55
Mean :38.44 Mean :485.7 Mean : 42.64
3rd Qu.:44.75 3rd Qu.:600.0 3rd Qu.: 33.62
Max. :76.02 Max. :900.0 Max. :150.00
NA's :3 NA's :6
> test[is.na(test)] <- 999
> summary(test)
mp tepl kryst
Min. : 7.11 Min. :100.0 Min. : 21.70
1st Qu.: 34.27 1st Qu.:400.0 1st Qu.: 25.93
Median : 41.75 Median :500.0 Median : 92.90
Mean :244.28 Mean :485.7 Mean :452.51
3rd Qu.: 70.05 3rd Qu.:600.0 3rd Qu.:999.00
Max. :999.00 Max. :900.0 Max. :999.00
>
> test[test>900] <- NA
> summary(test)
mp tepl kryst
Min. : 7.11 Min. :100.0 Min. : 21.70
1st Qu.:32.25 1st Qu.:400.0 1st Qu.: 24.15
Median :37.50 Median :500.0 Median : 26.55
Mean :38.44 Mean :485.7 Mean : 42.64
3rd Qu.:44.75 3rd Qu.:600.0 3rd Qu.: 33.62
Max. :76.02 Max. :900.0 Max. :150.00
NA's :3 NA's :6
>
> #Labeling categorical variable levels
> elsq2wbl$EVERRELJOB <- factor(elsq2wbl$EVERRELJOB, levels = c(0,1), labels =
> c("No","Yes"))
> elsq2wbl$PSWBL <- factor(elsq2wbl$PSWBL, levels = c(0,1), labels =
> c("No","Yes"))
>
> ##Trying to create a new variable to indicate if the student had a job
> #related to the college studies that was NOT a WBL experience
> elsq2wbl$NONWBLRELJOB <- ifelse(elsq2wbl$PSWBL=="No" &
> elsq2wbl$EVERRELJOB=="Yes",1,0)
You can use simple logical functions to get desired result
First sample data
> a <- sample(c("Y", "N"), 30, replace=TRUE)
> b <- sample(c("Y", "N"), 30, replace=TRUE)
> (a=="N")*(b=="Y")
[1] 1 1 0 0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1
has 1 only if both conditions are met.
and it works with NA values too.
> a[c(3,5,8)] <- NA
> b[c(3,6,7,8)] <- NA
> (a=="N")*(b=="Y")
[1] 1 1 NA 0 NA NA NA NA 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0
[26] 0 0 0 0 1
Cheers
Petr
>
> #Cross tab to check counts of two variables that new variable is based upon
> xtabs(~PSWBL+EVERRELJOB,subset(elsq2wbl,BYSCTRL==1&G10COHRT==1),add
> NA=TRUE)
>
> #Checking count of newly created variable
> Q2sub <- subset(elsq2wbl,BYSCTRL==1&G10COHRT==1)
> library(plyr)
> count(Q2sub,'NONWBLRELJOB')
>
> #The new variable has the correct count of "1", but 88 cases too many for "0"
> #The cross tab shows 20 and 68 NA cases that are being incorrectly counted as
> "0" in the new variable
>
> #My other approach at trying to handle the NAs properly-returns an error
> elsq2wbl$NONWBLRELJOB <- ifelse(elsq2wbl$PSWBL=="No" &
> elsq2wbl$EVERRELJOB=="Yes",1,ifelse(is.na(elsq2wbl$PSWBL)&is.na(elsq2wbl$
> EVERRELJOB),NA,
>
> ifelse(elsq2wbl$PSWBL!="No" & elsq2wbl$EVERRELJOB!="Yes",0)))
>
>
>
> Courtney Benjamin
>
> Broome-Tioga BOCES
>
> Automotive Technology II Teacher
>
> Located at Gault Toyota
>
> Doctoral Candidate-Educational Theory & Practice
>
> State University of New York at Binghamton
>
> cbenjami at btboces.org<mailto:cbenjami at btboces.org>
>
> 607-763-8633
>
> [[alternative HTML version deleted]]
>
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