the first. from SAS in R

Is there any similar function in R to the first. in SAS?

What it dose is:

Lets say we have this table:

?a b ?c
?1 1 ?5
?1 0 ?2
?2 0 ?2
?2 0 NA
?2 9 ?2
?3 1 ?3


and then I want do to do one thing the first time the number 1 appers in a
and something else the secund time 1 appers in a and so on.

so

something similar to:

if first.a {
?a$d<-1
}else{
?a$d<-0
}

This would give me

?a b ?c b
?1 1 ?5 1
?1 0 ?2 0
?2 0 ?2 1
?2 0 NA 0
?2 9 ?2 0
?3 1 ?3 1

Is there such a function in R or anything similar?


thx

//Joel

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Is there any similar function in R to the first. in SAS?

What it dose is:

Lets say we have this table:

 a b  c
 1 1  5
 1 0  2
 2 0  2
 2 0 NA
 2 9  2
 3 1  3


and then I want do to do one thing the first time the number 1  
appers in a
and something else the secund time 1 appers in a and so on.

so

something similar to:

if first.a {
a$d<-1
}else{
a$d<-0
}

Is there any similar function in R to the first. in SAS?

What it dose is:

Lets say we have this table:

 a b  c
 1 1  5
 1 0  2
 2 0  2
 2 0 NA
 2 9  2
 3 1  3


and then I want do to do one thing the first time the number 1 appers in a
and something else the secund time 1 appers in a and so on.

so

something similar to:

if first.a {
a$d<-1
}else{
a$d<-0
}

This would give me

 a b  c b
 1 1  5 1
 1 0  2 0
 2 0  2 1
 2 0 NA 0
 2 9  2 0
 3 1  3 1

Is there such a function in R or anything similar?

thx

//Joel

-- 
View this message in context: http://r.789695.n4.nabble.com/the-first-from-SAS-in-R-tp3055417p3055417.html
Sent from the R help mailing list archive at Nabble.com.

Interesting. Check this out:

u <- sample(c(TRUE, FALSE), 10, replace = TRUE)

u

[1] FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE

class(u)

[1] "logical"

u + 0

[1] 0 0 1 0 0 1 0 0 0 0

0 + u

[1] 0 0 1 0 0 1 0 0 0 0

v <- rpois(10, 3)

!duplicated(v)

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

class(!duplicated(v))

[1] "logical"

!duplicated(v) + 0

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

0 + !duplicated(v)

[1] 1 0 1 1 1 1 0 1 0 1

# Now assign !duplicated(v) to an object:

w <- !duplicated(v)
class(w)

[1] "logical"

0 + w

[1] 1 0 1 1 1 1 0 1 0 1

w + 0

[1] 1 0 1 1 1 1 0 1 0 1

I can see *what* is going on, but what is the reason for it? I see another
notebook entry coming :)

Dennis

On Tue, Nov 23, 2010 at 6:12 AM, David Winsemius <dwinsemius at comcast.net>wrote:

On Nov 23, 2010, at 8:33 AM, Joel wrote:

Is there any similar function in R to the first. in SAS?

What it dose is:

Lets say we have this table:

 a b  c
 1 1  5
 1 0  2
 2 0  2
 2 0 NA
 2 9  2
 3 1  3


and then I want do to do one thing the first time the number 1 appers in a
and something else the secund time 1 appers in a and so on.

so

something similar to:

if first.a {
a$d<-1
}else{
a$d<-0
}

The duplicated function which returns a logical vector with those features
can easily be coerced to numeric.

df$d <- as.numeric(!duplicated(df$a))


I was a bit puzzled about my failure to get coercion by the method which I
thought was supposed to work, namely adding 0.

df$e <- !duplicated(df$a)+0  # does not coerce

df$e <- 0 + !duplicated(df$a) # pre-adding 0 does coerce

Maybe the rules on coercion were amended.

--
David


 This would give me

 a b  c b
 1 1  5 1
 1 0  2 0
 2 0  2 1
 2 0 NA 0
 2 9  2 0
 3 1  3 1

Is there such a function in R or anything similar?


thx

//Joel

--
View this message in context:
http://r.789695.n4.nabble.com/the-first-from-SAS-in-R-tp3055417p3055417.html
Sent from the R help mailing list archive at Nabble.com.

David Winsemius, MD
West Hartford, CT

	[[alternative HTML version deleted]]

On Tue, 23 Nov 2010, Dennis Murphy wrote:

Interesting. Check this out:

u <- sample(c(TRUE, FALSE), 10, replace = TRUE)

u

[1] FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE

class(u)

[1] "logical"

u + 0

[1] 0 0 1 0 0 1 0 0 0 0

0 + u

[1] 0 0 1 0 0 1 0 0 0 0

v <- rpois(10, 3)

!duplicated(v)

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

class(!duplicated(v))

[1] "logical"

!duplicated(v) + 0

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

0 + !duplicated(v)

[1] 1 0 1 1 1 1 0 1 0 1

# Now assign !duplicated(v) to an object:

w <- !duplicated(v)
class(w)

[1] "logical"

0 + w

[1] 1 0 1 1 1 1 0 1 0 1

w + 0

[1] 1 0 1 1 1 1 0 1 0 1

I can see *what* is going on, but what is the reason for it? I see  
another
notebook entry coming :)

See

	?Arithmetic

and read the paragraph under Details starting 'Logical vectors'

On Nov 23, 2010, at 11:04 AM, Charles C. Berry wrote:

On Tue, 23 Nov 2010, Dennis Murphy wrote:

Interesting. Check this out:

u <- sample(c(TRUE, FALSE), 10, replace = TRUE)

u

[1] FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE

class(u)

[1] "logical"

u + 0

[1] 0 0 1 0 0 1 0 0 0 0

0 + u

[1] 0 0 1 0 0 1 0 0 0 0

v <- rpois(10, 3)

!duplicated(v)

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

class(!duplicated(v))

[1] "logical"

!duplicated(v) + 0

[1]  TRUE FALSE  TRUE  TRUE  TRUE  TRUE FALSE  TRUE FALSE  TRUE

0 + !duplicated(v)

[1] 1 0 1 1 1 1 0 1 0 1

# Now assign !duplicated(v) to an object:

w <- !duplicated(v)
class(w)

[1] "logical"

0 + w

[1] 1 0 1 1 1 1 0 1 0 1

w + 0

[1] 1 0 1 1 1 1 0 1 0 1

I can see *what* is going on, but what is the reason for it? I see 
another
notebook entry coming :)

See

 ?Arithmetic

and read the paragraph under Details starting 'Logical vectors'

Chuck;

Compare these three, all of which are using binary operators on logical 
vectors which is what is being discussed in ?Arithmetic:

 duplicated(c("a", "a", "b") ) + 0

[1] 0 1 0

 !duplicated(c("a", "a", "b") ) + 0

[1]  TRUE FALSE  TRUE

 0 + !duplicated(c("a", "a", "b") )

[1] 1 0 1

I believe the proper place to go is ?Syntax where operator precedence is 
discussed. I think the precendence rules implicitly do this in the second 
instance, because "+" has higher precendence than negation:

! ( duplicated(c("a", "a", "b") ) + 0 )

-- 
David.

Chuck

Dennis

On Tue, Nov 23, 2010 at 6:12 AM, David Winsemius 
<dwinsemius at comcast.net>wrote:

On Nov 23, 2010, at 8:33 AM, Joel wrote:

Is there any similar function in R to the first. in SAS?

What it dose is:

Lets say we have this table:

a b  c
1 1  5
1 0  2
2 0  2
2 0 NA
2 9  2
3 1  3


and then I want do to do one thing the first time the number 1 appers 
in a
and something else the secund time 1 appers in a and so on.

so

something similar to:

if first.a {
a$d<-1
}else{
a$d<-0
}

The duplicated function which returns a logical vector with those 
features
can easily be coerced to numeric.

df$d <- as.numeric(!duplicated(df$a))


I was a bit puzzled about my failure to get coercion by the method 
which I
thought was supposed to work, namely adding 0.

df$e <- !duplicated(df$a)+0  # does not coerce

df$e <- 0 + !duplicated(df$a) # pre-adding 0 does coerce

Maybe the rules on coercion were amended.

--
David


This would give me

a b  c b
1 1  5 1
1 0  2 0
2 0  2 1
2 0 NA 0
2 9  2 0
3 1  3 1

Is there such a function in R or anything similar?


thx

//Joel

--
View this message in context:
http://r.789695.n4.nabble.com/the-first-from-SAS-in-R-tp3055417p3055417.html
Sent from the R help mailing list archive at Nabble.com.

David Winsemius, MD
West Hartford, CT

 [[alternative HTML version deleted]]

Charles C. Berry                            Dept of Family/Preventive 
Medicine
cberry at tajo.ucsd.edu			    UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901

David Winsemius, MD
West Hartford, CT

Is there any similar function in R to the first. in SAS?

    ?duplicated

    a$d <- ifelse( duplicated( a$a ), 0 , 1 )

    a$d.2 <- as.numeric( !duplicated( a$a ) )

Actually, duplicated does not duplicate SAS' first. operator, though it
may suffice for the OP's needs.

To illustrate, let's start with a dataframe of 3 key columns and some data
in x:
tt <- data.frame(k1 = rep(1:3, each=10), k2 = rep(1:5, each=2, times=3),
k3=rep(1:2, times=15), x = 1:30)

# Try to mimic what the following SAS datastep would do,
# assuming 'tt' is already sorted:
#       data foo;
#         set tt;
#         by k1, k2;
#         put first.k1=, first.k2=;
#       run;

# SAS' first. operations would result in these values:
tt$sas.first.k1 <- rep(c(1, rep(0,9)), 3)
tt$sas.first.k2 <- rep(1:0, 15)

# R duplicated() returns these values.  You can see they
# are the same for k1, but dissimilar after row 10 for k2.
tt$duplicated.k1 <- 0+!duplicated(tt$k1)
tt$duplicated.k2 <- 0+!duplicated(tt$k2)

all.equal( tt$sas.first.k2, 0+!duplicated( tt[, c("k1","k2") ] ) )

# I've found I need to lag a column to mimic SAS' first.
# operator, thusly, though perhaps someone else knows
# differently.  Note this does not work on unordered
# dataframes!
lag.k1 <- c(NA, tt$k1[1:(nrow(tt) - 1)])
tt$r.first.k1 <- ifelse(is.na(lag.k1), 1, tt$k1 != lag.k1)

lag.k2 <- c(NA, tt$k2[1:(nrow(tt) - 1)])
tt$r.first.k2 <- ifelse(is.na(lag.k2), 1, tt$k2 != lag.k2)

Mimicking SAS' last. operation can be done in a similar manner, by
anti-laging the column of interest and changing the comparisons somewhat.

Enjoy the days,
cur
-- 
Curt Seeliger, Data Ranger
Raytheon Information Services - Contractor to ORD
seeliger.curt at epa.gov
541/754-4638

	[[alternative HTML version deleted]]

d <- data.frame(log=trunc(log(1:10)), sqrt=trunc(sqrt(1:10)))
within(d, first <- isFirstInRun(log))

# Or look for change in any number of vectors:
within(d, first <- isFirstInRun(log, sqrt)) # TRUE if either changes

-----Original Message-----
From: r-help-bounces at r-project.org 
[mailto:r-help-bounces at r-project.org] On Behalf Of 
Seeliger.Curt at epamail.epa.gov
Sent: Tuesday, November 23, 2010 10:38 AM
To: r-help at r-project.org
Cc: Joel
Subject: Re: [R] the first. from SAS in R

Is there any similar function in R to the first. in SAS?

    ?duplicated

    a$d <- ifelse( duplicated( a$a ), 0 , 1 )

    a$d.2 <- as.numeric( !duplicated( a$a ) )

Actually, duplicated does not duplicate SAS' first. operator, 
though it 
may suffice for the OP's needs.

To illustrate, let's start with a dataframe of 3 key columns 
and some data 
in x:
tt <- data.frame(k1 = rep(1:3, each=10), k2 = rep(1:5, 
each=2, times=3), 
k3=rep(1:2, times=15), x = 1:30)

# Try to mimic what the following SAS datastep would do, 
# assuming 'tt' is already sorted:
#       data foo;
#         set tt;
#         by k1, k2;
#         put first.k1=, first.k2=;
#       run;

# SAS' first. operations would result in these values:
tt$sas.first.k1 <- rep(c(1, rep(0,9)), 3)
tt$sas.first.k2 <- rep(1:0, 15)

# R duplicated() returns these values.  You can see they 
# are the same for k1, but dissimilar after row 10 for k2.
tt$duplicated.k1 <- 0+!duplicated(tt$k1)
tt$duplicated.k2 <- 0+!duplicated(tt$k2)

# I've found I need to lag a column to mimic SAS' first. 
# operator, thusly, though perhaps someone else knows 
# differently.  Note this does not work on unordered 
# dataframes!
lag.k1 <- c(NA, tt$k1[1:(nrow(tt) - 1)])
tt$r.first.k1 <- ifelse(is.na(lag.k1), 1, tt$k1 != lag.k1)

lag.k2 <- c(NA, tt$k2[1:(nrow(tt) - 1)])
tt$r.first.k2 <- ifelse(is.na(lag.k2), 1, tt$k2 != lag.k2)

Mimicking SAS' last. operation can be done in a similar manner, by 
anti-laging the column of interest and changing the 
comparisons somewhat.

Enjoy the days,
cur
-- 
Curt Seeliger, Data Ranger
Raytheon Information Services - Contractor to ORD
seeliger.curt at epa.gov
541/754-4638

	[[alternative HTML version deleted]]