ggplot with extracting rows from data frame in for loop, showing different colors

Question

I have a data frame that contains monthly time series data (from jan 2010 through dec 2012).

    df<- data.frame(code=NA,Year=NA,Month=rep(seq(as.Date('2010/1/1'),by='month',length.out=36),3),x1=rnorm(3*36))
    df$code[1:36]<-1; df$code[37:72]<-2; df$code[73:108]<-3
    yr <- c(rep(2010,12),rep(2011,12),rep(2012,12))
    df$Year<-rep(yr,3)

I would like to extract the rows that have the same code (there will be 36 rows for each code), and plot the values for each code on top of each other. I tried achieving this by the following code:

    m <- ggplot(df[1:36,], aes(x=Month,y=x1)) + geom_point() + geom_line(aes(color ='ID:1')) + 
    scale_x_date(labels = date_formatv(format = "%m"),breaks = date_breaks("month"))+ 
    xlab("") + ylab("")+ facet_wrap(~Year,scales=("free_x"))

Now I wrote a for loop to extract the next 36 observations and add them to the plot:

    for(i in 1:2){
      data2 <- df[((i*36)+1):((i+1)*36),]
      m<-m+geom_point(data=data2,aes(x=Month,y=x1))+geom_line(data=data2,aes(x=Month,y=x1
                                                                               ,color=paste0('ID:',i+1)))
   }

This code produces the following plot:

enter image description here

Now my questions are:

(1) As you can see, I don't get a legend for ID:2 (it only produces the legend for the last one), how can I get that?

(2) I would like to see different color for each code (associated with the legend), how can I achieve that?

(3) I am sure there should be a better way to produce the desired output, rather than using for loop, which is not recommended, any suggestion?

scoa · Accepted Answer · 2015-05-01 17:39:06Z

1

Map code to color to your aes statement.

m <- ggplot(df, aes(x=Month,y=x1,color=factor(code))) + 
  geom_point() + 
  geom_line() + 
  scale_x_date(labels = date_format(format = "%m"),breaks = date_breaks("month"))+ 
  xlab("") + ylab("")+ facet_wrap(~Year,scales=("free_x"))
m

edited May 1, 2015 at 17:39

answered May 1, 2015 at 17:21

scoa

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David Robinson · Accepted Answer · 2015-05-01 17:21:14Z

1

Instead of using a for loop or subsetting, add color = factor(code) to your aesthetics, which will add separately colored lines (and points) for each group of 36:

m <- ggplot(df, aes(x=Month, y=x1, color = factor(code))) +
    geom_point() + geom_line() + 
    scale_x_date(labels = date_format(format = "%m"),breaks = date_breaks("month"))+ 
    xlab("") + ylab("")+ facet_wrap(~Year,scales=("free_x"))

print(m)

enter image description here

(You could naturally customize the label title with something like labs(color = "ID"), or customize the choices of colors with scale_color_manual).

answered May 1, 2015 at 17:21

David Robinson

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