title: Make multiple separate plots from single data frame in R
body: <p>I have a large dataset that I would prefer not to split up because it will be rather time consuming. One column contains a list of parks which I want to make separate plots for as each plot belongs somewhere different. Each park needs to be grouped by Zone and Year as time series graphs. The mean for Height_mm also needs to be calculated with standard errors. There are 5 different parks each with 3 different zones and 10 different years. There are over 5000 records in the csv.</p>
  
  <pre><code>head(data)
  
    Park_name  Zone Year  Height_mm
  1     Park1 Zone1 2011        380
  2     Park1 Zone1 2011        510
  3     Park1 Zone1 2011        270
  4     Park1 Zone2 2011        270
  5     Park1 Zone2 2011        230
  6     Park1 Zone2 2011        330
  </code></pre>
  
  <p>I would like to be able to manipulate the code below to make this work though I just can't figure it out. I'll gladly take any other suggestions though. </p>
  
  <pre><code>library(ggplot2)
  library(plyr)
  
  data=read.table("C:/data.csv", sep=",", header=TRUE)
  
  ggplot(data, aes(x=Year, y=Height_mm)) + 
    #geom_errorbar(aes(ymin=mean-se, ymax=mean+se), width=.05, colour="black", position=pd) +
    geom_line() +
    geom_point(size=3, fill="black") +
    xlab("Year") + 
    ylab("Mean height (mm)") +
    #facet_wrap(~Park_name, scales = "free", ncol=2) + #I'd like something like this but with all plots as separate figures
    theme_bw() +
    theme(axis.text.x=theme_text(),  
          #axis.title.x=theme_blank(), 
          #axis.title.y=theme_blank(), 
          axis.line=theme_segment(colour="black"), 
          panel.grid.minor = theme_blank(),
          panel.grid.major = theme_blank(),
          panel.border=theme_blank(),
          panel.background=theme_blank(),
          legend.justification=c(10,10), legend.position=c(10,10), 
          legend.title = theme_text(),
          legend.key = theme_blank()
    )
  </code></pre>
  
  <p>I'm assuming I need a 'for' loop of some kind though I don't know where to put it or how to use it. Thanks</p>