[R] Non-Parametric Adventures in R

[Jamesp]

I just started using R and I'm having all sorts of "fun" trying different
things.

I'm going to document the different things I'm doing here as a kind of case
study.  I'm hoping that I'll get help from the community so that I can use R
properly.

Anyways, in this study, I have demographic data, drug usage data, and side
effect data.  All of this is loaded into a csv file.  I'm using Rweb as an
interface, so I had to modify the cgi-bin code slightly, but it works pretty
well.  I'm looking for frequency counts, some summary data for columns where
it makes sense, plots and X-squared tests.  My data frame is named X since
that's what Rweb names it.

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1) I was thinking I'd have to go through each nominal variable (i.e.
table(X$race) ), but I think I have it figured out now.  summary(X) is nice,
but I need to recode nominal data with labels so the results are meaningful.

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2) I had an issue with multiple plots overwriting each other, and I managed
to bypass that with:
par(mfrow=c(2,1))
I have to update it to correspond to the number of plots I think.  There's
probably a better way to do this.

barplot(table(X$race))  prints out a barplot so that's great 

-----------------------------------------------------------------------------------------------------
3) I was able to code my data so it shows up in tables better with
X$race <- factor(X$race, levels = c(0,2), labels = c("African
American","White,Non-Hispanic"))

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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4) The coding for all of my drug variables is identical, and I'd like to
create a loop that goes through and labels accordingly

I'm not having good success with this yet, but here's what I'm trying.

X[1,] <- factor(X[1,], levels = c(0,1,2,3,4,5), labels= c("none","last
week","last 3 month","last year","regular use at least 3 months","unknown
length of usage"))

I know I would need to replace the [1,] with something that gives me the
column, but I'm not sure what to put syntactically at the moment.

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5) I had more success creating new variables based on the old ones.  So I
end up with yes/no answers to drug usage

for (i in 24:56)
{
  X[,i+173] <- ifelse(X[,i] >0,c(1),c(0))
}

I'd like to have been able to make a new variable name based off of the old
variable name (i.e. dropping "_when" from the end of each and replace it
with "_yn")

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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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6)  I'm able to make a cross-tabulated table and perform a X-squared test
just fine with my recoded variable

table(X$race,X[,197])
prop.test(table(X$race,X[,197]))

but I would like to be able to do so with all of my drugs, although I can't
seem to make that work

for (i in 197:229)
{
  table(X$race,X[,i])
  prop.test(table(X$race,X[,i]))
}

-------------------------------------------------------------------------------------------------

Thanks for reading over this and I do appreciate any help.  I understand
that there's "an R way" of doing things, and I look forward to learning the
method.
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