R help - Jun 2014 - Loops to produce plots and leyend

I've tried several things but I don't manage to get this plot right. Any
help greatly appreciated!
I'm running a for loop to produce 4 plots at once. Each plot should only 
show data points for a specific group (i.e. 4 plots for groups 1 to 4). 
The coordinates of the points should be petal length and width. The 
colour of these points should codify the species variable. Finally I'd 
like to show a legend for the colours on these plots. It's important 
that each species has a unique colour. Thanks you a lot for your input!

     # Data
     dd <- iris

     dd$group <- ifelse(dd$Sepal.Length>=4.3 & dd$Sepal.Length<5.2,
1,
                          ifelse(dd$Sepal.Length>=5.2 & 
dd$Sepal.Length<6.1, 2,
                                 ifelse(dd$Sepal.Length>=6.1 & 
dd$Sepal.Length<7, 3,
                                        ifelse(dd$Sepal.Length>=7, 4, NA))))
     dd$group <- as.integer(dd$group)

     dd$Species <- c(rep("Wild", 12), rep("Pinky", 12),
rep("Orangy",
12), rep("Smelly", 12),
                     rep("Pretty", 12), rep("Blue", 12),
rep("Big", 12),
rep("Rare", 12),
                     rep("Toxic", 12), rep("Danger", 12), 
rep("Abundant", 18), rep("Last", 12))


     # Code to plot 4 graphs. It doesn't work!
     pdf("plot_test.pdf", width=10, height=10)
     par(mfrow=c(2, 2))
     for(b in unique(dd$group)){
       idx <- dd$group==b
       plot(dd$Petal.Length, dd$Petal.Width, ty="n", 
xlim=range(dd$Petal.Length), ylim=range(dd$Petal.Width))
       cols <- as.numeric(unique(dd$Species))
       points(dd$Petal.Length[idx], dd$Petal.Width[idx],
              col=cols[as.numeric(dd$Species[idx])])
       legend("right", legend=unique(dd$Species[idx]), pch=1, 
col=cols[as.numeric(unique(dd$Species[idx]))])
     }
     dev.off()

On Jun 20, 2014, at 9:18 AM, Bea GD wrote:
> I've tried several things but I don't manage to get this plot
right. Any help greatly appreciated!
> I'm running a for loop to produce 4 plots at once. Each plot should
only show data points for a specific group (i.e. 4 plots for groups 1 to 4). The
coordinates of the points should be petal length and width. The colour of these
points should codify the species variable. Finally I'd like to show a legend
for the colours on these plots. It's important that each species has a
unique colour. Thanks you a lot for your input!
> 
>    # Data
>    dd <- iris
> 
>    dd$group <- ifelse(dd$Sepal.Length>=4.3 &
dd$Sepal.Length<5.2, 1,
>                         ifelse(dd$Sepal.Length>=5.2 &
dd$Sepal.Length<6.1, 2,
>                                ifelse(dd$Sepal.Length>=6.1 &
dd$Sepal.Length<7, 3,
>                                       ifelse(dd$Sepal.Length>=7, 4,
NA))))
>    dd$group <- as.integer(dd$group)
> 
>    dd$Species <- c(rep("Wild", 12), rep("Pinky",
12), rep("Orangy", 12), rep("Smelly", 12),
>                    rep("Pretty", 12), rep("Blue", 12),
rep("Big", 12), rep("Rare", 12),
>                    rep("Toxic", 12), rep("Danger", 12),
rep("Abundant", 18), rep("Last", 12))
> 
> 
>    # Code to plot 4 graphs. It doesn't work!
>    pdf("plot_test.pdf", width=10, height=10)
>    par(mfrow=c(2, 2))
>    for(b in unique(dd$group)){
>      idx <- dd$group==b
>      plot(dd$Petal.Length, dd$Petal.Width, ty="n",
xlim=range(dd$Petal.Length), ylim=range(dd$Petal.Width))
>      cols <- as.numeric(unique(dd$Species))
>      points(dd$Petal.Length[idx], dd$Petal.Width[idx],
>             col=cols[as.numeric(dd$Species[idx])])
>      legend("right", legend=unique(dd$Species[idx]), pch=1,
col=cols[as.numeric(unique(dd$Species[idx]))])
>    }
>    dev.off()
This appears to be a duplicate of
http://stackoverflow.com/questions/24333076/for-loop-to-produce-plots-with-legend
and is already answered. You are requesten not to corss-post to SO and Rhelp.
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html

-- 
David Winsemius
Alameda, CA, USA