Programmatically create arguments to data.frame in R

Question

this is probably a really stupid question, but I am big R newbie and. I have a matrix, which i need to frame. Is there a better way to do this, other than:

data1 = data.frame(X0 = Ytrain, X1 = Xtrain[,2], X2 = Xtrain[,3], ... , X50 = Xtrain[,51])

?

I was able to generate this monstrosity in Emacs, but now i need to create R function that does this. Any help would be greatly appriciated.

Tomas

Could you give a little more info about Ytrain and Xtrain? You write that you have a matrix, which I assume is Xtrain. Is Ytrain also a matrix? Or do both objects come from one original matrix? I ask because Ytrain might get recycled if it is shorter than nrow(Xtrain). — BenBarnes
– BenBarnes, Commented Jul 11, 2012 at 11:58
Yeah, i forgot to mention that. Ytrain is a column vector with same amount of rows as teh Xtrain. But guys below already figured that out. — Arg
– Arg, Commented Jul 11, 2012 at 11:59

A5C1D2H2I1M1N2O1R2T1 · Accepted Answer · 2012-07-11 11:57:40Z

3

This ought to do it:

# Assuming you used all the columns of `Xtrain` but the first
NEW.DF <- data.frame(Ytrain, Xtrain[, -1]) 
# If you didn't use all the cols of `xtrain`:
# NEW.DF <- data.frame(Ytrain, Xtrain[, 2:51])
names(NEW.DF) <- paste0("X", 0:(ncol(NEW.DF)-1))

edited Jul 11, 2012 at 11:57

A5C1D2H2I1M1N2O1R2T1

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answered Jul 11, 2012 at 11:40

Tyler Rinker

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6 Comments

A5C1D2H2I1M1N2O1R2T1 Over a year ago

+1 (to help you get that silver R badge....). But according to the OP, Xtrain starts from the second column, so you should modify your answer accordingly.

Tyler Rinker Over a year ago

Was taking care of that as you were typing :) Thanks

Arg Over a year ago

not sure if it was a typo, but i had to use paste("X", 0:(ncol(NEW.DF)-1),sep="") ... no biggie, though

BenBarnes Over a year ago

@Arg, the function paste0 was added in R 2.15.0 and is equivalent to the way you used paste.

Arg Over a year ago

aha, that explains it. I use 2.14.1.

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A5C1D2H2I1M1N2O1R2T1 · Accepted Answer · 2012-07-11 11:52:25Z

2

data1 <- cbind(data.frame(X0 = Ytrain),data.frame(Xtrain[, -1]))

Matrix columns are named X1...XN by default on conversion to data.frame unless they are already named.

edited Jul 11, 2012 at 11:52

A5C1D2H2I1M1N2O1R2T1

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answered Jul 11, 2012 at 11:40

James

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