[R] recoding data with loops

From: Donald Braman <donald.braman_at_gmail.com>
Date: Mon, 19 May 2008 15:41:40 -0400

# I'm new to R and am trying to get the hang of how it handles
# dataframes & loops. If anyone can help me with some simple tasks,
# I'd be much obliged.

# First, i'd like to generate some random data in a dataframe
# to efficiently illustrate what I'm up to.
# let's say I have six variables as listed below (I really
# have hundreds, but a few will illustrate the point).
# I want to generate my dataframe (mdf)
# with the 6 variables X 100 values with rnorm(7).
# How do I do this? I tried many variations on the following:

for(i in 1:length(var_list)) {var_list[1] <- rnorm(100)} mdf <- data.frame(cbind(varlist[1:length(var_list)]) mdf

# Then, I'd like to recode the variables that begin with the letter "H".
# I've tried many variations of the following, but to no avail:

reverse_list <- c("HEQUAL", "HREVDIS1", "HREVDIS2") reversed_list <- c("RHEQUAL", "RHREVDIS1", "RHREVDIS2") for(i in 1:length(reverse_list))
 {mdf[ ,e_reversed_list][[i]] <- recode(mdf[ ,e_reverse_list][[i]], '5:99=NA; 1=4; 2=3; 3=2; 4=1; ', as.factor.result=FALSE)

# I'm sure I have many deep misunderstandings about the R language, but
# if I can get this much done, I think I'll be well on my way to
understanding R
# and how it works with loops and dataframes.

# Thanks!

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