# Re: [R] two newbie questions

From: jim holtman <jholtman_at_gmail.com>
Date: Sun, 22 Jun 2008 18:59:24 -0400

This does away with the 'for' loops and uses 'expand.grid' to create the combinations. I think I got the right variables substituted:

my.df <- data.frame(replicate(10, round(rnorm(100, mean=3.5, sd=1)))) var.list <- c("dv1", "dv2", "dv3", "iv1", "iv2", "iv3", "iv4", "iv5", "intv1", "intv2")
names(my.df) <- var.list

# I have some are DVs:
dvs <- c("dv1", "dv2", "dv3")

# some IVs:
ivs <- c("iv1", "iv2", "iv3", "iv4", "iv5")

# and some binary interaction variables: intvs <- c("intv1", "intv2")
library(car)
my.df[intvs] <- lapply(my.df[intvs], function(x)  recode(x, recodes = "lo:3.5=0; 3.5:hi=1; ",as.factor.result = FALSE))

# now I loop through a series of interactions using the vector numbers: # create a dataframe of values to check

```xpnd <- expand.grid(dvs, ivs, intvs) # create combinations
invisible(apply(xpnd, 1, function(.row) {
jpeg(paste(paste(.row, collapse="_"),".jpg", sep=''))

my.fit <- lm( my.df[[.row]] ~ my.df[[.row]] + my.df[[.row]] +
my.df[[.row]]:my.df[[.row]])
```
colors <- ifelse (my.df[[.row]] == 1, "black", "grey")    plot(my.df[[.row]], my.df[[.row]], xlab=.row,

ylab=.row, col=colors, pch=".")    curve (cbind (1, 1, x, 1*x) %*% coef(my.fit), add=TRUE, col="black")    curve (cbind (1, 0, x, 0*x) %*% coef(my.fit), add=TRUE, col="gray")

dev.off()
}
))

On Sun, Jun 22, 2008 at 6:26 PM, Donald Braman <dbraman_at_law.gwu.edu> wrote:
> # I've tried to make this easy to paste into R, though it's probably
> so simple you won't need to.
> # I have some data (there are many more variables, but this is a
> reasonable approximation of it)
>
> # here's a fabricated data frame that is similar in form to mine:
> my.df <- data.frame(replicate(10, round(rnorm(100, mean=3.5, sd=1))))
> var.list <- c("dv1", "dv2", "dv3", "iv1", "iv2", "iv3", "iv4", "iv5",
> "intv1", "intv2")
> names(my.df) <- var.list
>
> # I have some are DVs:
> dvs <- c("dv1", "dv2", "dv3")
>
> # some IVs:
> ivs <- c("iv1", "iv2", "iv3", "iv4", "iv5")
>
> # and some binary interaction variables:
> intvs <- c("intv1", "intv2")
> library(car)
> my.df[intvs] <- lapply(my.df[intvs], function(x)
> recode(x, recodes = "lo:3.5=0; 3.5:hi=1; ",as.factor.result = FALSE))
>
> # now I loop through a series of interactions using the vector numbers:
> for(dv in 1:3) {
> for(iv in 4:8) {
> for (intv in 9:10) {
> jpeg(paste(names(my.df[iv]), names(my.df[dv]), names(my.df[intv]),
> ".jpg", sep="_"))
> with(data.frame(my.df), {
> my.fit <- lm( my.df[[dv]] ~ my.df[[iv]] + my.df[[intv]] +
> my.df[[iv]]:my.df[[intv]])
> colors <- ifelse (my.df[[intv]] == 1, "black", "grey")
> plot(my.df[[iv]], my.df[[dv]], xlab=names(my.df[iv]),
> ylab=names(my.df[dv]), col=colors, pch=".")
> curve (cbind (1, 1, x, 1*x) %*% coef(my.fit), add=TRUE, col="black")
> curve (cbind (1, 0, x, 0*x) %*% coef(my.fit), add=TRUE, col="gray")
> })
> dev.off()
> }
> }
> }
>
>
> # Question1: Works fine, but using the vector numbers feels kludgy --
> especially if the variables in question aren't consecutive.
> # Is there a more elegant way of doing this with my lists of variable
> names? Something like this, for example:
> for(dv in dvs) {
> for(iv in ivs) {
> for (intv in intvs) {
> jpeg(paste(dv, iv, intv, ".jpg", sep="_"))
> with(data.frame(my.df), {
> my.fit <- lm(my.df[dv] ~ my.df[iv] + my.df[intv] + my.df[iv]:my.df[intv])
> colors <- ifelse (my.df[[intv]] == 1, "black", "grey")
> plot(my.df[iv], my.df[dv], xlab=iv, ylab=names(dv), col=colors, pch=".")
> curve (cbind (1, 1, x, 1*x) %*% coef(my.fit), add=TRUE, col="black")
> curve (cbind (1, 0, x, 0*x) %*% coef(my.fit), add=TRUE, col="gray")
> })
> dev.off()
> }
> }
> }
>
> # Clearly that's wrong -- why it's wrong is obscure to me, though!
>
> # Question2: Could this could be done by using "apply" rather than a loop?
> # Or is looping better here bc there are several actions performed at
> each iteration?
> # I'm still trying to get my head around all the ways to ditch looping in R.
>
>
> Donald Braman
> http://www.law.gwu.edu/Faculty/profile.aspx?id=10123
> http://research.yale.edu/culturalcognition
> http://ssrn.com/author=286206
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

```--
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

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