Hello, everybody
Say I have
nm1 <- c(rep(1,10), rep(0,10))
then I can do:
diff(nm1)
to see where I have shift in value
but what if I have
nm2 <- c(rep("SPZ8", 10), rep("SPX9", 10))
how can I produce the same ouput as diff(nm1) does, that is zeros
everywhere except for one place where SPZ8 changes to SPX9 (there
should be 1 there)?
What if I have a matrix of characters like that:
nm3 <- c(rep("GLF9", 4), rep("GLF10", 16))
matr <- cbind(nm2, nm3)
How can I efficiently create two more columns that contain zeros
everywhere except for place where there is shift in character values?
Thanks for help!
Sergey
--
I'm not young enough to know everything. /Oscar Wilde
Experience is one thing you can't get for nothing. /Oscar Wilde
When you are finished changing, you're finished. /Benjamin Franklin
Tell me and I forget, teach me and I remember, involve me and I learn.
/Benjamin Franklin
Luck is where preparation meets opportunity. /George Patten
2009/3/13 Sergey Goriatchev <sergeyg at gmail.com>:> Say I have > nm1 <- c(rep(1,10), rep(0,10)) > then I can do: > diff(nm1) > to see where I have shift in value > > but what if I have > nm2 <- c(rep("SPZ8", 10), rep("SPX9", 10)) > > how can I produce the same ouput as diff(nm1) does, that is zeros > everywhere except for one place where SPZ8 changes to SPX9 (there > should be 1 there)? > > What if I have a matrix of characters like that: > nm3 <- c(rep("GLF9", 4), rep("GLF10", 16)) > matr <- cbind(nm2, nm3) > > How can I efficiently create two more columns that contain zeros > everywhere except for place where there is shift in character values?You could convert to "factor" and then to numeric: > nm2 <- c(rep("SPZ8", 10), rep("SPX9", 10)) > diff(as.numeric(as.factor(nm2))) [1] 0 0 0 0 0 0 0 0 0 -1 0 0 0 0 0 0 0 0 0 It might be that your character values should really be factors anyway - check out some R docs on what factors are and what they can do for you. That also means you might want your matrix to be a data frame, since a matrix can't contain your character values and numeric 0/1 values. Data frames can! If you try it with a matrix you end up getting character zeroes and minus ones: > matr <- cbind(nm2, nm3) > matr = cbind(matr,c(0,diff(as.numeric(as.factor(matr[,1]))))) > matr[8:12,] nm2 nm3 [1,] "SPZ8" "GLF10" "0" [2,] "SPZ8" "GLF10" "0" [3,] "SPZ8" "GLF10" "0" [4,] "SPX9" "GLF10" "-1" [5,] "SPX9" "GLF10" "0" Easier with factors in data frames: > df=data.frame(nm2=as.factor(nm2),nm3=as.factor(nm3)) > df$dnm2 = c(0,diff(as.numeric(df$nm2))) > df[8:12,] nm2 nm3 dnm2 8 SPZ8 GLF10 0 9 SPZ8 GLF10 0 10 SPZ8 GLF10 0 11 SPX9 GLF10 -1 12 SPX9 GLF10 0 Barry
Hi:
For A, you can use head and tail but you have to add a zero the front.
For B, you can use the same function, but put it inside an sapply and
run over the columns and then cbind it back with the original dataframe.
A)
nm2 <- c(rep("SPZ8", 10), rep("SPX9", 10))
-1.0*c(0,as.numeric((head(nm2,-1) != tail(nm2,-1))))
B)
nm3 <- c(rep("GLF9", 4), rep("GLF10", 16))
matr <- cbind(nm2, nm3)
temp<-as.data.frame(sapply(1:ncol(matr), function(.col) {
-1.0*c(0,as.numeric((head(matr[,.col],-1) != tail(matr[,.col],-1))))
}))
cbind(matr,temp)
On Fri, Mar 13, 2009 at 5:24 AM, Sergey Goriatchev wrote:
> Hello, everybody
> Say I have nm1 <- c(rep(1,10), rep(0,10)) then I can do: diff(nm1) to
> see where I have shift in value
> but what if I have nm2 <- c(rep("SPZ8", 10),
rep("SPX9", 10))
> how can I produce the same ouput as diff(nm1) does, that is zeros
> everywhere except for one place where SPZ8 changes to SPX9 (there
> should be 1 there)?
> What if I have a matrix of characters like that: nm3 <-
c(rep("GLF9",
> 4), rep("GLF10", 16)) matr <- cbind(nm2, nm3)
> How can I efficiently create two more columns that contain zeros
> everywhere except for place where there is shift in character values?
> Thanks for help! Sergey
> --
> I'm not young enough to know everything. /Oscar Wilde Experience is
> one thing you can't get for nothing. /Oscar Wilde When you are
> finished changing, you're finished. /Benjamin Franklin Tell me and I
> forget, teach me and I remember, involve me and I learn. /Benjamin
> Franklin Luck is where preparation meets opportunity. /George Patten
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