Priya Bhatt
2012-May-16 08:07 UTC
[R] Help needed for efficient way to loop through rows and columns
Dear R-helpers:
I am trying to write a script that iterates through a dataframe that looks
like this:
Example dataset called "sample":
names <- c("S1", "S2", "S3", "S4")
X <- c("BB", "AB", "AB", "AA")
Y <- c("BB", "BB", "AB", "AA")
Z <- c("BB", "BB", "AB", NA)
AorB <- c("A", "A", "A", "B")
sample <- data.frame(names, X, Y, Z, AorB)
for a given row,
if AorB == A, then AA == 2, AB = 1, BA = 1, BB = 0
if AorB == B, then AA == 0, AB = 1, BA = 1, BB = 2
I've been trying to write this using apply and ifelse statements in hopes
that my code runs quickly, but I'm afraid I've make a big mess. See
below:
apply(sample, 1, function(i) {
ifelse(sample$AorB[i] == "A",
(ifelse(sample[i,] == "AA", sample[i,] <- 2 ,
ifelse(sample[i,] == "AB" || sample[i,] ==
"BA" ,
sample[i,] <- 1,
ifelse(sample[i,] == "BB", sample[i,] <- 0,
sample[i,] <- NA )) )
) , ifelse(sample$AorB[i,] == "B"),
(ifelse(sample[i,] == "AA", sample[i,] <- 0 ,
ifelse(sample[i,] == "AB" || sample[i,] ==
"BA" ,
sample[i,] <- 1,
ifelse(sample[i,] == "BB", sample[i,] <- 2,
sample[i,] <- NA))))) })
Any Advice?
[[alternative HTML version deleted]]
David L Carlson
2012-May-16 13:53 UTC
[R] Help needed for efficient way to loop through rows and columns
Can you show us what you want the final data.frame to look like? You've created five variables stored as factors and you seem to be trying to change those to numeric values? Is that correct? Since AB and BA are always set to 1, you could just replace those values globally rather than mess with the ifelse commands for those values. Only AA and BB are affected by the value of AorB. Your apply() function processes the data.frame by row so i is a vector consisting of all the values in the row. You seem to be coding as if i was a single integer (as in a for loop). ---------------------------------------------- David L Carlson Associate Professor of Anthropology Texas A&M University College Station, TX 77843-4352> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- > project.org] On Behalf Of Priya Bhatt > Sent: Wednesday, May 16, 2012 3:08 AM > To: r-help at r-project.org > Subject: [R] Help needed for efficient way to loop through rows and > columns > > Dear R-helpers: > > I am trying to write a script that iterates through a dataframe that > looks > like this: > > > Example dataset called "sample": > > names <- c("S1", "S2", "S3", "S4") > X <- c("BB", "AB", "AB", "AA") > Y <- c("BB", "BB", "AB", "AA") > Z <- c("BB", "BB", "AB", NA) > AorB <- c("A", "A", "A", "B") > > sample <- data.frame(names, X, Y, Z, AorB) > > > for a given row, > > if AorB == A, then AA == 2, AB = 1, BA = 1, BB = 0 > > if AorB == B, then AA == 0, AB = 1, BA = 1, BB = 2 > > I've been trying to write this using apply and ifelse statements in > hopes > that my code runs quickly, but I'm afraid I've make a big mess. See > below: > > apply(sample, 1, function(i) { > > > ifelse(sample$AorB[i] == "A", > (ifelse(sample[i,] == "AA", sample[i,] <- 2 , > ifelse(sample[i,] == "AB" || sample[i,] == "BA" , > sample[i,] <- 1, > ifelse(sample[i,] == "BB", sample[i,] <- 0, > sample[i,] <- NA )) ) > ) , ifelse(sample$AorB[i,] == "B"), > (ifelse(sample[i,] == "AA", sample[i,] <- 0 , > ifelse(sample[i,] == "AB" || sample[i,] == "BA" , > sample[i,] <- 1, > ifelse(sample[i,] == "BB", sample[i,] <- 2, > sample[i,] <- NA))))) }) > > > Any Advice? > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code.
Rui Barradas
2012-May-16 14:15 UTC
[R] Help needed for efficient way to loop through rows and columns
Hello,
Your data.frame is composed exclusively of factors, but try this
(I've changed the name to 'sampl', because 'sample' is an R
function.)
# logical index vectors
iA <- sampl$AorB == "A"
iB <- sampl$AorB == "B"
new.sampl <- data.frame(
apply(sampl, 2, function(x){
iAA <- x == "AA"
iBB <- x == "BB"
x[ iA & iAA ] <- 2
x[ iA & iBB ] <- 0
#
x[ iB & iAA ] <- 0
x[ iB & iBB ] <- 2
#
x[ x %in% c("AB", "BA") ] <- 1
x}
))
Hope this helps,
Rui Barradas
Priya Bhatt wrote>
> Dear R-helpers:
>
> I am trying to write a script that iterates through a dataframe that looks
> like this:
>
>
> Example dataset called "sample":
>
> names <- c("S1", "S2", "S3",
"S4")
> X <- c("BB", "AB", "AB", "AA")
> Y <- c("BB", "BB", "AB", "AA")
> Z <- c("BB", "BB", "AB", NA)
> AorB <- c("A", "A", "A", "B")
>
> sample <- data.frame(names, X, Y, Z, AorB)
>
>
> for a given row,
>
> if AorB == A, then AA == 2, AB = 1, BA = 1, BB = 0
>
> if AorB == B, then AA == 0, AB = 1, BA = 1, BB = 2
>
> I've been trying to write this using apply and ifelse statements in
hopes
> that my code runs quickly, but I'm afraid I've make a big mess.
See
> below:
>
> apply(sample, 1, function(i) {
>
>
> ifelse(sample$AorB[i] == "A",
> (ifelse(sample[i,] == "AA", sample[i,] <- 2 ,
> ifelse(sample[i,] == "AB" || sample[i,] ==
"BA" ,
> sample[i,] <- 1,
> ifelse(sample[i,] == "BB", sample[i,]
<- 0,
> sample[i,] <- NA )) )
> ) , ifelse(sample$AorB[i,] == "B"),
> (ifelse(sample[i,] == "AA", sample[i,] <- 0 ,
> ifelse(sample[i,] == "AB" || sample[i,] ==
"BA" ,
> sample[i,] <- 1,
> ifelse(sample[i,] == "BB", sample[i,]
<- 2,
> sample[i,] <- NA))))) })
>
>
> Any Advice?
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@ mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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