Hi Sharad,
See ?paste, particularly the 'collapse' argument:
>
mols=c("LEPTIN","SAA","PTH","sEGFR")
> paste(mols[1:3], collapse = " + ")
[1] "LEPTIN + SAA + PTH"
If this is going to ultimately end up in regression (my spidey sense
is tingling), the follow up question you will have is something like:
"I have a bunch of string variables that I am trying to use in a
formula in lm() but it isn't work".
then there will be a series of possible hacks to shoehorn character
data into the formula. Here is a pre-emptive suggestion (of many
possibilities) using the mtcars dataset in R. Suppose 'mpg' is always
the outcome, and then you want all sets of 2 predictors:
## make a data frame where each column represents all the variables
for one model
varset <- data.frame(rbind("mpg", combn(colnames(mtcars)[-1], 2)),
stringsAsFactors = FALSE)
## looks like this:> varset[, 1:3]
X1 X2 X3
1 mpg mpg mpg
2 cyl cyl cyl
3 disp hp drat
## fit a separate model of mpg regressed on every other variable in the dataset
## but subset mtcars by each column of varset
## store results in one big list
allmodels <- lapply(varset, function(i) {
lm(mpg ~ ., data = mtcars[, i])
})
## extract all coefficients into a matrix
sapply(allmodels, coef)
note that with this general method I am proposing, all models need not
have the same number of predictors. I just did it for convenience so
I could use the combn() function to generate a bunch of combinations.
Cheers,
Josh
On Wed, Oct 26, 2011 at 6:03 PM, 1Rnwb <sbpurohit at gmail.com>
wrote:> Hello gurus,
>
> I have some variables, and i am creating combinations for analysis in the
> end i need these variables to be displayed like "LEPTIN+SAA+PTH".
currently
> i am using loop to perform this. I would appreciate any pointers to do it
> without the loop.
>
>>
mols=c("LEPTIN","SAA","PTH","sEGFR")
>> samples=mols[1:3]
>> samples
> [1] "LEPTIN" "SAA" ? ?"PTH"
>> names1=samples[1]
>> ?for (j in 2:length(samples)){ names1 = paste (names1, samples[j],
>> sep="+")}
>> names1
> [1] "LEPTIN+SAA+PTH"
>>
> thanks
> sharad
>
> --
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--
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, ATS Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/